which is kind of shocking because I feel like lemmy is one of the fediverse "replacements" that most easily replaces.

I feel like most others don't always "scratch that itch" that some of there closed source rivals do. But honestly the only thing at this point imo that lemmy has going against it is the smaller user base and therefore lack of as niche of communities

Lemmy is still very much in its infancy. It's not even reached version 1.0 yet. While we've all been on here for a while now, its future is still very much uncertain and hasn't seen anywhere near the adoption that Mastodon and other microblog Fedi platforms have.