It's obviously no reddit in size, very far from it, but it's by no means empty either.
The "threadiverse" is the current "growth" area of the fediverse IMO, especially if you include blogs like WP and Ghost. See eg: https://community.nodebb.org/post/99736
Getting involved and supporting that kind of platform on the fediverse is IMO a good idea. The fediverse needs more "community building" tools, and forums/reddits are good for that. Lemmy even has private sub-lemmies on the road map.