I call this the new social death spiral. When meta-discussion dominates for too long, it kills the community. I'm surprised Mastodon has lasted for as long as it has for precisely this reason.
But that's not an interesting topic to discuss, at least not for very long. A community based on negativity towards an existing community is built on sand, and probably isn't going to last very long.
So they need to find a way to attract people who discussing 'normal' things, and don't spend every waking moment of their life being obsessed with the platform/the old platform.
That matches my subjective perception. Activity has significantly waned again. Larger communities are good (e.g. !europe@feddit.de). Smaller ones (e.g. !rpg@ttrpg.network) were good but are dying now.
It would be good timing for another exodus scandal by Reddit now.