Anything that isn’t in the current mainstream tends to be in short supply on Lemmy. People haven’t gotten used to the idea that other people aren’t already running those communities for them. I think they’re still working up the bravery to be more active/figuring out the platform a d if it’s worth the effort.

As others suggested you could start some communities up yourself. Maybe another option is digging up some of the dead communities and making a post asking others if they’re interested in taking them over? That’s worked for a couple communities in the past.