The problem I expect a useful study of metaethics to solve is "How do we compellingly demonstrate that moral language (that is, our use of words like 'good,' 'bad,' 'right,' 'wrong,' 'should,' and 'ought') can be cashed out entirely in non-moral terms (e.g., in terms of expected and realized value of actions) with nothing important left over?"
Or, if we can't solve that one, then: "After we cash out moral language into non-moral terms as far as we can, what exactly is left over, and what is interesting about that stuff?"
It's not clear to me that this is entirely a task for evo psych, as what seems to happen is that regardless of what evo psych demonstrates, people who believe moral language cannot be cashed out in non-moral terms will simply deny that evo psych's claims are at all relevant.
Ditto for every field of study other than morality itself.
Of course, if I already believe that moral language can be cashed out in non-moral terms, there are several positions I can take:
"How do we compellingly demonstrate that moral language (that is, our use of words like 'good,' 'bad,' 'right,' 'wrong,' 'should,' and 'ought') can be cashed out entirely in non-moral terms (e.g., in terms of expected and realized value of actions) with nothing important left over?"
Why not conduct an experiment and stop using 'moral language' for a week and see if you hit upon something that is inexpressible without it?
lukeprog gave a list of metaethics questions here:
Most of these questions make no sense to me. I imagine that the moral intuitions in my brain come from a special black box within it, a "morality core" whose outputs I cannot easily change. (Explaining how my "morality core" ended up a certain way is a task for evo psych, not philosophy.) Or I can be more enlightened and adopt Nesov's idea that the "morality core" doesn't exist as a unified device, only as an umbrella name for all the diverse "reasons for action" that my brain can fire. Either perspective can be implemented as a computer program pretty easily, so I don't feel there's any philosophical mystery left over. All we have is factual questions about how people's "morality cores" vary in time and from person to person, how compelling their voices are, finding patterns in their outputs, etc. Can someone explain what problem metaethics is supposed to solve?