Lemmy doesn't have the niche communities that Reddit did, and those come with a larger user base.
Lemmy has plenty of memes, politics, Linux, and anime, but there are many small communities which do not (yet) have active equivalents here.
Here are a few of my own examples, but everyone will have their own unique list: r/wheresthebeef, r/Penderwicks, r/twistypuzzles, r/Cubers, r/fusion, r/legoRockets, r/HarryPotteronHBO, r/anarchycubing, r/deextinction, r/cubinggore.
I would welcome more users if it means more niche communities.