>>83714927/aco/ is an amazing example of how board culture, more than anything else, determines subject matter. Ideally, /aco/ is just NSFW /co/, but there were two problems: the furry ban applies there, removing a huge chunk of /co/ works. And the mods on /d/ decided this was the perfect time to go full bore on the "western /d/ images need not apply" rule. I suppose that actually makes it more rule than board culture determined, but the second rule feels a lot like a board culture thing. It was only sparringly enforce on /d/. Plenty of people could post western shit just fine, and then sometimes it'd be very strictly enforced.
So /aco/ was left bereft of a lot of /co/ people who decided not to use it and it was taken over by /d/ people exiled from /d/ and all to willing to finally have a place to post their western images without playing the "is the mod gonna be cool?" roulette. And this further discouraged /co/ people from participating.
And now we have /trash/ for all the furry and worse stuff. There's no real place for lewd discussions to go but /co/, the very problem that made people want an /aco/ to begin with. Storytimes still show up on /aco/, or at least they did.