I think--but do not know with certainty--that the users of the "old" style forums, the ones that became well-known and well used 15-20 years ago have aged, and some have moved on to other interests.
Many of the younger people interested in photography use the Instagram-style social media model when they think of internet socializing (and commercial self-promotion) on the subject of photography.
I see quite a bit of 'Photographers of Threads" on the social media site/app Threads, which I mainly read for social/political/current events commentary.
(Threads is Meta's copy of Twitter's micro-blog setup, but so far without the disimprovements made when the the current owner took over Twitter in late 2022) Threads has a fairly active photo crowd which seems to skew younger. Lots of "youngsters" (people in their 20's and 30's) excitedly posting their latest film and digital shots. Some of great interest, some not, many styles are posted. Most viewing of Threads, X (the former Twitter,) Instagram, and the like is done on smartphone screens, but for the photography, is better viewed on larger tablet/laptop/desk monitors.