The phrase "task for evo psych, not philosophy" is an invitation to false dichotomies. Ditto for "all we have is factual questions." Sure, evo psych could shed some light on the sources of many ethical intuitions. So could neuropsych, and plain old psych, and cultural anthropology, and game theory, and logic. And then we'll face questions of which ethical responses we want to trust or keep and which we want to change, and again we'll turn to science, and to everyday experience - but that doesn't mean we're not doing philosophy. It only means that we're doing it right.
Similarly, epistemology asks questions that merit scientific inquiry, with a heavy contribution from psychology. But that doesn't mean epistemology is not philosophy, nor that it is all nonsense.
CharlesR has replied with a point-by-point clarification of the questions metaethics is supposed to solve. Is that helpful?
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?