Some of the more niche communities I had on reddit don't exist on Lemmy yet, and likely won't for the foreseeable future. DPS chasing for a small MMO seems like a thing that could exist here, but for now the majority of the public would just use Reddit or whatever instead.
The custom mtg card community I joined is pretty much just dead. I did a card a day for a while in there, but then I ran out of cards is already made and now it's just sitting again.
Other than that, the general purpose of it is doing exactly what Reddit did for me, so...