Try fiddling around with your language settings maybe? Sometimes the language filter can hide posts in a weird way.

Ultimately, if your only interest is in a handful of niche communities, then Lemmy isn’t quite there yet, I agree. I am also missing a bunch of niche communities, but I enjoy most of the popular content that’s on Lemmy anyhow, so I’m not too bothered by the loss of the niche stuff for now.