I never found “all” browsable for any platform whether it be lemmy, YouTube, or reddit. It’s why subscribing has been so important to me, and filtering. Like on YouTube which I access through freetube I’ve disabled “trending” and “popular” since even the thumbnails were obnoxious for majority of the videos, and I blocked out channels to keep them from dominating search results. And on reddit what even made /r/all viewable was a reddit enhancement suite filter lists that was in the hundreds for blocking of communities, and even then was a wack a mole that required keyword filtering.

All of any platform will devolve into a shit show. As for niche subs. Yeah, not much that can be done about that if the user base is small.