Seems like lemmy.ml is really collapsing in on itself. Overall not good for the general health of the fediverse.

I'd argue that a biased overly-centralized instance like that collapsing in on itself is good for the general health of the Fediverse.

there needs to be some kind of accountability/ redress if open & free communities are going to be a long term project.

The redress is having lots of servers to switch to, much like how on Reddit the redress was "start your own subreddit if the one you're on is moderated poorly." I can't imagine any system that would let you "take control" of some other instance without that being ridiculously abusable.