I don't this question is generally addressable without discussing your meta-ethical views.
If welfare is good because (and only because) we as individuals care about our welfare (call this Premise C) then things being good requires actual people (whether past/present/future) to exist in the first place - otherwise there is no source of value, and no basis on which to judge what is good and what is not.
Note that this isn't necessarily constructivism, insofar as you will have something like "X is …
One challenge to Premise C is the temporary depressive. Suppose Adam doesn't care about his welfare, and is considering suicide. He also has access to a 100% reliable antidepressant pill. If he takes the pill, he will have a very happy future (which he would, at that future time, highly value). But right now, he doesn't value that at all. So he commits suicide instead. Did Adam make a mistake? I think yes: he should've taken the pill and had a happy future instead. C implies no.
The Adam case works as an intuition pump, but it falls short of being an argument. For someone inclined to accept C, it's pretty easy to accept that Adam didn't make a mistake.
On the moral realism thing — it may be true that your normative claims can be separated from your moral realism, but your writing style is so pervaded by realist turns of phrase that it's easy to see why people keep picking up on that and assuming that your realism is central to your argument. For example:
Hmm, I think it would be difficult to do normative ethics in a way that didn't sound at least superficially "realist". That's part of why anti-realists like Blackburn and Gibbard have put so much work into showing that their metaethics is compatible with "talking like a realist". So I think I'd rather just urge anti-realist readers to shed their unnecessary suspicion of objectively-tinged moral discourse.
I guess what strikes me as objectionable is the conjunction of realism with the sort of strong confidence in your own normative views (and dismissal of other views) that you express in this post.
Suppose I find myself in in the following situation:
(1) I believe there is a true, objectively correct axiology.
(2) I sometimes encounter otherwise reasonable-seeming people who have thought carefully about the relevant issues and concluded that there is no strong reason to prefer utopia over the barr…
See 'Knowing What Matters' - https://philpapers.org/rec/CHAKWM - where I set out my normative epistemology, including an explanation of why actual disagreement is irrelevant. (You could have "otherwise reasonable-seeming people" who think that torture is the only good, so either moral realists can have default trust in their normative intuitions -- including about which other views are outright crazy -- or they're inevitably led to full-blown skepticism, which I think is plainly far worse.)
The section in that paper on "when actual disagreement matters" is a bit brief, so I'm not sure I fully understand the position you sketch there. It seems to be something like "disagreement matters when it is non-ideal, and we can hope to resolve it through clarifying arguments; but if there are fundamentally different worldviews, we can expect the arguments to be dialectically unsatisfying, so we don't need to worry about it too much."
Is that a fair summary? I so, I think it's a pragmatically …
Yep, fair summary! In general (including, e.g., external world skepticism) I don't think it's possible to present non-question-begging counterarguments against radical skepticism. We can just explain why we reject some of the skeptic's premises (as I do in response to Street earlier in the paper -- see especially my discussion of the "moral lottery"), and hence why we aren't ourselves committed to sharing their skepticism. For more on my generally anti-skeptical approach to philosophy, see: h…
Regarding skepticism, I think Moorean responses fail pretty hard in the face of moral disagreement. It is as if I say "here is one hand, here is another," and my apparently good-faith interlocutor replys "I agree the first thing is a hand, but the second is obviously an octopus; but don't worry, you really do have another hand, it's right there!" [points at my shoe] — enough experiences of this type, would (and perhaps should?) push me towards skepticism concerning the existence and knowability of an external material world.
So, hooray for fallibilism! (But also: Boo for indecisiveness!)