This. All of us Reddit Refugees (me included) fucked up when we arrived and put the cart before the horse. Lemmy is like a small town; you may simply not get all the specific communities you want, but there's probably somebody with a similar enough interest that they'll talk to you about the stuff you like, and they probably have things that you would like to talk about if you saw it. Higher-level categories should do fine unless and until a certain type of content starts to annoy other users by its sheer prevalence.

As someone else said, Lemmy is the niche community.