From my PoV:

1. The activity around memes, image sharing, memes, shitposting, memes, memes, and memes have not felt too different from Reddit, but unsurprising as it's very easy to consume content
2. The typical communities that have coalesced in a grassroots fashion are thriving well as long as one can accept there's a lot of duplicate threads (like the Twitter related stuff in technology communities). Some communities are populated by Reddit content porting bots and these feel so barren because it's a wall of submissions with a small number of comments each and the bot owners have no visible intent to stop.
3. Niche communities are incredibly quiet. That's understandable but also unfortunate, more so if it is a niche community that did not move over.

Things will hopefully get better with time.