Hello and welcome! If I can be forgiven for tooting my own horn, I (with Lee Sharkey) wrote a detailed series of forum posts "High Time For Drug Policy Reform" back in August 2017, which primarily focused on the potential of psychedelics as a treatment for mental health. I also mentioned it a promising area in an EAGlobal talk in 2018.

To address your point, I think the reason more EAs don't pay attention to psychedelics is a combination of EAs not thinking mental health is an important problem (something I've also written about) and because psychedelics are weird and unfamiliar. Regarding mental health's importance, I think EAs are increasingly interested in the longterm (this would also explain a relative lack of interest in poverty and animal welfare) or they are focused on poverty but don't believe mental health treatments are comparably cost-effective with anti-poverty ones. I think mental health treatments are comparably cost-effective - at least in the same ballpark although it's unclear which is better on current evidence - when we use self-reported happiness scores to judge effectiveness. You might then doubt we can sensibly measure happiness, which I argue we can in this forum post.

You forgot ibogaine, which seems to be the most compelling example. According to lots of anecdotes across the internet, it reliably cures decades old addictions to heroin in a single sitting.

Still I don't think psychedelic use is necessarily a good thing. It makes people more open to experience, which for some will be a door to madness. See for example Scott Alexander's writings about it

MDMA is beginning Phase 3 trials for the treatment of PTSD.

Flagging that both MDMA & psilocybin have received "breakthrough therapy" designation from the FDA.

(MDMA through the work of MAPS; psilocybin through the work of Compass Pathways.)

I wonder how the flow-through effects of psychedelics and their normalisation compare to other interventions. My intuition suggests that the flow through effects are large.

Some speculations:

• people tend to make big decisions: this leads to larger consequences, especially if those people are influential. I expect psychedelics and other first-world interventions to have larger flow-through effects because more influential people are affected. Compare changing the life of an American politician vs. saving the life of a Ugandan farmer.
• people come up with new and creative ideas. In Pollan's book there's a reference to the idea that psychedelics increase the rate of mutation of ideas. Yes, a lot of these are bad/useless ideas, but some are good/useful. Which ones spread depends on the selection filter (i.e. the epistemic hygiene of the community). But even useful ideas can be harmful. Do we really want general faster intellectual and technological progress; will the progress be general or will it affect certain domains more than others?
• people seem to become more active and ambitious (and thus change more in their environment). I'm not sure how desirable this is. That depends on the difficulty of cooperating and coordinating with them, and also on the danger of a less stable system (I'm assuming more ambition leads to more change and less stability, but even this may be wrong if people act to increase resilience and enforce the current system. The latter seems unlikely in the case of psychedelics however.)

These flow-through effects may be bigger (and I'm already quite uncertain about this) but they are not necessarily positive. They also increase altruism, which is probably good, although ambitious and uninformed altruism is probably worse than doing nothing at all.

I'm curious why psychedelics aren't talked about more...

For me, because I didn't know. Insofar as evidence exists, I'm interested. [Edit: to be an EA focus area, it would have to score well in the importance/tractability/neglectedness framework - might tractability be a problem here?]

I imagine drugs are a more political realm than EA usually goes for, but there are various reasons to build up expertise in political areas - communication, persuasion, lobbying - beyond this particular cause area.

"I'm curious why psychedelics aren't talked about more..." I see psychedelics as a depression or addiction treatment as interesting, but not competitive with, say, bednets. You're welcome to try to change my view.