Basically all of the subs that reddit shut down or are severely limited in scope. It's not my interests that are necessarily missing but what attracts people to a site is the ability to grow a community and I don't think people are going to wait two weeks on an essentially dead website to make the subreddit they want to curate. Reddit already exists, people like the functionality they just hate the censorship. I think just recreating reddit just without nazi mods is a pretty good tagline for user growth.