I post here when I make images, it's sort of part of my image-posting routine
Also, I have occasionally gotten good, actionable feedback that has helped me. I've just not had time to do much artwork at all recently; primarily doing coding.
Since GIMP's devs said (many years ago now) that they focus more on image manipulation rather than image creation, I've mostly moved over to other programs though. I still use GIMP, but most of my work is done in OSS programs dedicated to creation, like MyPaint and Krita.
Having followed many forums in a range of topics over the years, I have observed that they tend to have a 'lifetime' of sorts - they rise, become popular and then gradually fade away. Not having active admins is the killer, honestly, because mods can generally not update the underlying code. I guess more persistent forms of media tend to be larger and commercially run, having all sorts of topics on the same platform rather than focusing on a single niche.