My experience is that Lemmy is decent for tech-related stuff but outside of that, it can be difficult to find active communities depending on the hobby. I just went looking for a good Spanish learning or general language learning community and the few that I found have been inactive for months. Maybe I wasn’t looking in the right place (I searched in Communities > All).

I don’t think maximum growth should be a goal for Lemmy, I just think it needs a critical mass of activity to keep it interesting. Currently I think we just about have that for many tech/FOSS related topics but not so much outside it. The problem, I think, is that a lot of people who aren’t into tech/FOSS issues don’t know about Lemmy and don’t see why they wouldn’t just use Reddit or Discord.