Same here. One of the biggest issues is that Lemmy is currently terrible at surfacing content from niche communities: no weighted activity, no “multi-reddit-syle” community grouping - pretty much any main view mode is dominated by a few large communities only. This makes the death of the small communities a self-fulfilling prophecy.
The next version of Lemmy is making some very tepid improvements in that regard, but it’s nowhere near enough.