I find moral realism meaningful for each individual (you can evaluate choices according to my values applied with infinite information and infinite resources to think),
I can how that could be implemented. However, I don't see how that would count as morality. It amounts to Anything Goes, or Do What Thou Wilt. I don't see how a world in which that kind of "moral realism" holds would differ from one where moral subjectivism holds, or nihilism for that matter.
but I don't find it meaningful when applied to groups of people, all with their own values.
Where meaningful means implementable? Moral realism is not many things, and one of the things it is not is the claim that everyone gets to keep all their values and behaviour unaltered.
Not "anything goes, do what you will", so much as "all X go, X is such that we want X before we do it, we value doing X while we are doing it, and we retrospectively approve of X after doing it".
We humans have future-focused, hypothetical-focused, present-focused, and past-focused motivations that don't always agree. CEV (and, to a great extent, moral rationality as a broader field) is about finding moral reasoning strategies and taking actions such that all those motivational systems will agree that we Did a Good Job.
That said, being ...
There seems to be a widespread impression that the metaethics sequence was not very successful as an explanation of Eliezer Yudkowsky's views. It even says so on the wiki. And frankly, I'm puzzled by this... hence the "apparently" in this post's title. When I read the metaethics sequence, it seemed to make perfect sense to me. I can think of a couple things that may have made me different from the average OB/LW reader in this regard: