It’s having federation and stability issues right now because it’s so ridiculously big.

Lemmy hasn’t yet been optimized to handle so many users on a single server.

And yeah, the discoverability/finding communities to join is the weakest part of the Fediverse right now. You have to go to lemmyverse.net to search for communities across all instances and see their actual total member count, which isn’t very user friendly and needs to be integrated into Lemmy itself like this GitHub issue says