I used to hang out on a car forum and a car detailing forum. This was peak forums era - probably 2005 - 2010. The traffic on those sites is probably a tenth of what they used to have, in part, because that specific car model went out of production and there are always bigger and better cars to move on to. I think the detailing site went bust mostly because the professional personality moved on to another company and people followed him.
The hosts / owners of those sites tried to migrate/integrate secondary hosting via social media platforms which never really worked well at all as they don't have the necessary functionality of what a forum offers.
ATBS, a sports forum still makes sense to me because the content or product around which it's based never expires.