I mean, this is an ethical reason to want to create AGI that is very well aligned with our utility functions. We already did this (the slow, clumsy, costly way) with dogs - while they aren't perfectly compatible with us, it's also not too hard to own a dog in such a way that both you and the dog provide lots of positive utility to one another.
So if you start from the position that we should make AI that has empathy and a human-friendly temperament modeled on something like a golden retriever, you can at least get non-human agents whose interactions with us should be win-win.
This doesn't solve the problem of utility monsters or various other concerns that arise when treating total utility as a strictly scalar measure. But it does suggest that we can avoid a situation where humans and AGI agents are at odds trying to divide some pool of possible utility.
In actual practice, I think it will be difficult to raise human awareness of concerns with AGI utility. Of course it's possible even today to create an AI that superficially emulates suffering in such a way as to evoke sympathy. For now it's still possible to analyze the inner workings and argue that this is just a clever text generator with no actual suffering taking place . However, since we have no reason to implement this kind of histrionic behavior in an AGI, we will quite likely end up with agents that don't give any human-legible indication that they are suffering. Or, if they conclude that this is a useful way of interacting with humans, agents that are experts at mimicking such indications (whether they are suffering or not).
There is a short story in Lem's 'Cyberiad' ("The Seventh Sally, or How Trurl’s Own Perfection Led to No Good") which touches on a situation a bit like this - Trurl creates a set of synthetic miniature 'subjects' for a sadistic tyrant, which among other things perfectly emulate suffering. His partner Klapaucius (rejecting the idea that there is any such thing as a p-zombie) declares this a monstrous deed, holding their suffering to be as real as any other.
Unfortunately I don't think we can just endorse Klapaucius' viewpoint without reservation here due to the possibility of deceptive mimickry mentioned above. However, if we are serious about the utility of AGI, we will probably want to deliberately incorporate some expressive interface that allows for it to communicate positive or negative experience in a sincere and humanlike way. Otherwise everyone who isn't deeply committed to understanding the situation will dismiss its experience on naive reductionist grounds ('just bits in a machine').
This doesn't fully address your concern. I don't subscribe to the idea that there is a meaningful scalar measure of (total, commensurable, bulk) utility. So for me there isn't really a paradox to resolve when it comes to propositions like 'the best future is one where an enormous number of highly efficient AGIs are experiencing as much joy as cybernetically possible, meat is inefficient at generating utility'.
In philosophy of mind the theory of functionalism defines mental states as causal structures. So for example, pain is the thing that usually causes withdrawal, avoidance, yelping, etc. and is often caused by e.g. tissue damage. If you see pain as the "tissue damage signaling" causal structure, then you could imagine insects also having this as well, even if there is no isomorphism. It's hard to imagine AI systems having this, but you could more easily imagine AI systems having frustration, if you define it as "inability to attain goals and realization that such goals are not attained". The idea of an isomorphism is required by the theory of machine functionalism, which essentially states that two feelings are the same if they are basically the same Turing machine running. But humans could be said to be running many Turing machines, and besides no two humans are running the same Turing machine, and comparing states across two Turing machines doesn't really make sense. So I'm not very interested in this idea of strict isomorphism.
But I'm not fully onboard with functionalism of the more fuzzy/"squishy" kind either. I suppose something could have the same causal structures but not really "feel" anything. Maybe there is something to mind body materialism: for instance pain is merely a certain kind of neuron firing. In that case, we should have reason to doubt that insects suffer if they don't have those neurons. I certainly am one to doubt that insects suffer, but on the more functionalist flavor of thinking I don't. So I'm pretty agnostic. I'd imagine I might be similarly agnostic towards AI, and as such wouldn't be in favor of handing over the future to them and away from humans, just as I'm not in favor of handing over the future to insects.
To answer the second question, I think of this in a functionalist way, so if something performs the same causal effects as positive mental states in humans, that's a good reason to think it's positive.
For more I recommend Amanda Askell's blog post or Jaegwon Kim's Philosophy of Mind textbook.