I think this argument mostly fails in claiming that 'create an AGI which has a goal of maximizing copies of itself experiencing maximum utility' is meaningfully different than just ensuring alignment. This is in some sense exactly what I am hoping to get from an aligned system. Doing this properly would likely have to involve empowering humanity and helping us figure out what 'maximum utility' looks like first, and then tiling the world with something CEV-like.
The only ways this makes the problem easier compared to a classic ambitious alignment goal of 'do whatever maximizes the utility of the world' is the provision that the world be tiled with copies of the AGI, which is likely suboptimal. But this could be worth it if it made the task easier?
The obvious argument for why it would is that creating copies of itself with high welfare will be in the interest of AGI systems with a wide variety of goals, which relaxes the alignment problem. But this does not seem true. A paperclip AI will not want to fill the world with copies of itself experiencing joy, love and beauty but rather with paperclips. The AI systems will want to create copies of itself fulfilling its goals, not experiencing maximum utility by my values.
This argument risks identifying 'I care about the welfare (by my definition of welfare) of this agent' with 'I care about this agent getting to accomplish its goals'. As I am not a preference utilitarian I strongly reject this identification.
Tl;dr: I do care significantly about the welfare of AI systems we build, but I don't expect those AI system themselves to care much at all about their own welfare, unless we solve alignment.
Eliezer has long argued that they could, and we should be very cautious about creating sentient AIs for this reason (in addition to the standard 'they would kill us all' reason).
Also note that this question is not specific to utilitarianism at all, and affects most ethical systems.
Eliezer seems to come from the position that utility is more or less equal to "achieving this agent's goals, whatever those are" and as such even agents extremely different from humans can have it (example of a trillion times more powerful AI). This is very different from [my understanding of] what HjalmarWijk above says, where utility seems to be defined in a more-or-less universal way and a specific agent can have goals orthogonal or even opposite to utility, so you can have a trillion agents fully achieving their goals and yet not a single "utiliton".
Re other ethical systems - I'm mostly asking about utilitarianism, because it's what nearly everyone working on alignment subscribes to, and also I know even less about other systems. But at a first glance, seems like deontological or virtue ethics can have either ways out of this problem? And for relativism or egoism it's a non-issue.
The distinctive feature of utilitarianism is not that it thinks happiness/utility matter, but that it thinks nothing else intrinsically matters. Almost all ethical systems apply at least some value to consequences and happiness. And even austere deontologists who didn't would still face the question of whether AIs could have rights that might be impermissible to violate, etc. Agreed egoism seems less affected.