I had a quick look, and most of those seem to be niches that can’t be filled until we reach a higher population.
100% agree. And I know it first hand with [email protected]: it could be much larger as one just easily see when comparing with the similar reddit sub, but we don't share the same user base to begin with ;)
As it is I don't think we need more communities. We need more active members and simpler way to promote specific content. Like I said in my other answer, for me the real issue is there: for something that is proud to be 'federated', linking anywhere from anywhere should be rock solid and dead simple. It is not, far from it. If it's even doable. Heck, even within my own community: I don't know how I can safely put links to any previous thread or message in a thread that I'm sure will work for anyone clicking them no matter the instance they're logged in.
Maybe I'm missing something obvious and it's already a thing? But I think getting that ability to link stuff would be a huge win for Lemmy, no mater the number of active members ;)