The vast majority of communities are user-created, so it's kind of expected that there would be a long tail of community size, especially since there aren't any

The vast majority of communities are user-created, so it's kind of expected that there would be a long tail of community size, especially since there aren't any "default" communities like on Reddit. I think the most popular communities are still fairly active. I'm confident that there'll be more activity now that more people are joining.