One thing to note:

Engagement will always be better on new platforms, because they a) have no bots and b) haven't been growth hacked to death, since the strategies that work haven't been figured out yet.

These start at 0, then increase. When both of those trends grow strong enough, people start to leave in droves.

I know I did. On X, I used it a lot, then left when the bad algo content era began. On Insta, the engagement bait was bad enough when I joined that it deterred me from ever seriously using it.

I would expect these to become more of a problem over time, though I'm optimistic Bluesky can do better at beating them than other platforms have.