My sense of what is happening regarding discussions of EA and systemic change is:

• Actual EA is able to do assessments of systemic change interventions including electoral politics and policy change, and has done so a number of times
• Empirical data on the impact of votes, the effectiveness of lobbying and campaign spending work out without any problems of fancy decision theory or increasing marginal returns
• E.g. Andrew Gelman's data on US Presidential elections shows that given polling and forecasting uncertainty a marginal vote in a swing state average something like a 1 in 10 million chance of swinging an election over multiple elections (and one can save to make campaign contributions
• 80,000 Hours has a page (there have been a number of other such posts and discussion, note that 'worth voting' and 'worth buying a vote through campaign spending or GOTV' are two quite different thresholds) discussing this data and approaches to valuing differences in political outcomes between candidates; these suggest that a swing state vote might be worth tens of thousands of dollars of income to rich country citizens
• But if one thinks that charities like AMF do 100x or more good per dollar by saving the lives of the global poor so cheaply, then these are compatible with a vote being worth only a few hundred dollars
• If one thinks that some other interventions, such as gene drives for malaria eradication, animal advocacy, or existential risk interventions are much more cost-effective than AMF, that would lower the value further except insofar as one could identify strong variation in more highly-valued effects
• Experimental data on the effects of campaign contributions suggest a cost of a few hundred dollars per marginal vote (see, e.g. Gerber's work on GOTV experiments)
• Prediction markets and polling models give a good basis for assessing the chance of billions of dollars of campaign funds swinging an election
• If there are increasing returns to scale from large-scale spending, small donors can convert their funds into a small chance of huge funds, e.g. using a lottery, or more efficiently (more than 1/1,000 chance of more than 1000x funds) through making longshot bets in financial markets, so IMR are never a bar to action (also see the donor lottery)
• The main thing needed to improve precision for such estimation of electoral politics spending is carefully cataloging and valuing different channels of impact (cost per vote and electoral impact per vote are well-understood)
• More broadly there are also likely higher returns than campaign spending in some areas such as think tanks, lobbying, and grassroots movement-building; ballot initiative campaign spending is one example that seems like it may have better returns than spending on candidates (and EAs have supported several ballot initiatives financially, such as restoration of voting rights to convicts in Florida, cage bans, and increased foreign spending)
• A recent blog post by the Open Philanthropy Project describes their cost-effectiveness estimates from policy search in human-oriented US domestic policy, including criminal justice reform, housing reform, and others
• It states that thus far even ex ante estimates of effect there seem to have only rarely outperformed GiveWell style charities
• However it says: "One hypothesis we’re interested in exploring is the idea of combining multiple sources of leverage for philanthropic impact (e.g., advocacy, scientific research, helping the global poor) to get more humanitarian impact per dollar (for instance via advocacy around scientific research funding or policies, or scientific research around global health interventions, or policy around global health and development). Additionally, on the advocacy side, we’re interested in exploring opportunities outside the U.S.; we initially focused on U.S. policy for epistemic rather than moral reasons, and expect most of the most promising opportunities to be elsewhere. "
• Let's Fund's fundraising for climate policy work similarly made an attempt to estimate the impacts of their proposed intervention in this sort of fashion; without endorsing all the details of their analysis, I think it is an example of EA methodologies being quite capable of modeling systemic interventions
• Animal advocates in EA have obviously pursued corporate campaigns and ballot initiatives which look like systemic change to me, including quantitative estimates of the impact of the changes and the effects of the campaigns
• The great majority of critics of EA invoking systemic change fail to present the simple sort of quantitative analysis given above for the interventions they claim, and frequently when such analysis is done the intervention does not look competitive by EA lights
• A common reason for this is EAs taking into account the welfare of foreigners, nonhuman animals and future generations; critics may propose to get leverage by working through the political system but give up on leverage from concern for neglected beneficiaries, and in other cases the competition is interventions that get leverage from advocacy or science combined with a focus on neglected beneficiaries
• Sometimes systemic change critiques come from a Marxist perspective that assumes Marxist revolution will produce a utopia, whereas empirically such revolution has been responsible for impoverishing billions of people, mass killing, the Cold War, (with risk of nuclear war) and increased tensions between China and democracies, creating large object-level disagreements with many EAs who want to accurately forecast the results of political action
• Nonetheless, my view is that historical data do show that the most efficient political/advocacy spending, particularly aiming at candidates and issues selected with an eye to global poverty or the long term, does have higher returns than GiveWell top charities (even ignoring nonhumans and future generations or future technologies); one can connect the systemic change critique as a position in intramural debates among EAs about the degree to which one should focus on highly linear, giving as consumption, type interventions
• E.g. I would rather see $1000 go to something like the Center for Global Development, Target Malaria's gene drive effort, or the Swiss effective foreign aid ballot initiative than the Against Malaria Foundation
• I do think it is true that well-targeted electoral politics spending has higher returns than AMF, because of the impacts of elections on things such as science, foreign aid, great power war, AI policy, etc, provided that one actually directs one's efforts based on the neglected considerations
• EAs who are willing to consider riskier and less linear interventions are mostly already pursuing fairly dramatic systemic change, in areas with budgets that are small relative to political spending (unlike foreign aid),
• Global catastrophic risks work is focused on research and advocacy to shift the direction of society as a whole on critical issues, and the collapse of human civilization or its replacement by an undesirable successor would certainly be a systemic change
• As mentioned previously, short-term animal EA work is overwhelmingly focused on systemic changes, through changing norms and laws, or producing technologies that would replace and eliminate the factory farming system
• A number of EA global poverty focused donors do give to organizations like CGD, meta interventions to grow the EA movement (which can eventually be cashed in for larger systemic change), and groups like GiveWell or the Poverty Action Lab
• Although there is a relative gap in longtermist and high-risk global poverty work compared to other cause areas, that does make sense in terms of ceiling effects, arguments for the importance of trajectory changes from a longtermist perspective, and the role of GiveWell as a respected charity evaluator providing a service lacking for other areas
• Issue-specific focus in advocacy makes sense for these areas given the view that they are much more important than the average issue and with very low spending
• As funding expands in focused EA priority issues, eventually diminishing returns there will equalize with returns for broader political spending, and activity in the latter area could increase enormously: since broad political impact per dollar is flatter over a large range political spending should either be a very small or very large portion of EA activity
• Essentially, the cost per vote achieved through things like campaign spending is currently set by the broader political culture and has the capacity to absorb billions of dollars at similar cost-effectiveness to the current level, so it should either be the case that EA funds very little of it or enormous amounts of it
• There is a complication in that close elections or other opportunities can vary the effectiveness of political spending over time, which would suggest saving most funds for those
• The considerations are similar to GiveDirectly: since cash transfers could absorb all EA funds many times over at similar cost-effectiveness (with continued rapid scaling), it should take in either very little or almost all EA funding; in a forced choice it should either be the case that most funding goes to cash transfers, whereas for other interventions with diminishing returns on the relevant scale as mixed portfolio will yield more impact
• For now areas like animal advocacy and AI safety with budgets of only tens of millions of dollars are very small relative to political spending, and the impact of the focused work (including relevant movement building) makes more of a difference to those areas than a typical difference between political candidates; but if billions of dollars were being spent in those areas it would seem that political activity could be a competitive use (e.g. supporting pro-animal candidates for office)

Regarding increasing marginal returns (IMR), which seems to be the primary contribution of this paper and not obviously addressed by replies to other types of systemic change objections:

Perhaps rather than 'Are IMR commonly found in cause areas?', I would ask 'where are IMR found?' and, for the purposes of testing the critique, 'in which cases are relevant actors not already aware of those IMR?' This is because I expect the prevalence of IMR to vary substantially between areas. (I see that you also call for concrete examples in your paper.) Some examples, sorted from strategic to individual decision-making:

• DMR at a high level within causes: you may have seen this list of reasons to expect DMR when looking at a cause area at a sufficiently high level. I would argue that since
• the methodology you point to is largely about high-level cause prioritisation, and
• the neglectedness criterion works if there are roughly† logarithmic diminishing marginal returns within causes,
• the IMR objection does not apply to them.
• IMR when starting new projects: in their 2011 post on why they are not using donation matching, GiveWell discusses 'coordination matching', where the project only goes ahead if sufficient funds are committed (like Kickstarter), as a legitimate form of donation matching. [Minor: this may be IMR only with respect to money ultimately committed. A large donor making a partial, initial commitment may in fact have outsized impact relative to later funders due to the earlier donor causing later donors to act.]
• IMR when coordinating individual careers: this section of William MacAskill's 2017 EAGx Berlin talk encourages more attention to coordinated action. This includes things closely analogous to the coordination games you discuss in the paper, in which one person switching to their comparative advantage is a cost, but two people switching is a gain. I would guess that you would also like 80,000 Hours' writing on comparative advantage and other coordination concepts.

Of course, my examples of IMR are drawn from people who helped create the effective altruism community, so they help with 'where are IMR found?' but not with identifying points where IMR are underappreciated by the community. It certainly seems possible that there are issues I am unaware of. I see that in your paper you mention 'the problem of competition between NGOs and states' as a problem for which the solution which might have IMR. To rehash an old counterargument, I would guess that this is not really a conflict, in that substantially reducing disease prevalence (the relevant comparable on the scale of the funding required for other mass empowerment efforts) is hugely empowering. However, this is an off-the-cuff comment. I also know little about the example of whether corporate campaigns accelerate or decelerate abolition, but I believe that this was and probably still is an active debate among effectiveness-focused animal advocates.

† In fact, I am a little worried that the logarithmic assumption is sufficiently wrong to cause problems, while I am confident that there is DMR in general at this level.

I don't see that IMR poses any challenge to the standard EA cause prioritization method. IMR can be easily modeled as a tractability function that is increasing for some part of its domain. Depending on funding levels, causes with IMR can have the highest marginal utility per dollar, and hence would be prioritized according to the standard framework.