People on 4chan don't just complain, entire board subcultures have completely vanished along with the people in them. For example, /u/ used to be the unofficial lesbian advice and discussion board, and there was an entire community there co-existing happily with the porn posters and seekers. Got wiped out overnight by a new mod who decided the board should be solely for yuri porn, pissing off everyone in the process - and now the /u/ culture of that time is dead, with no record it ever even existed. (moot added a proper board for LGBT discussions a few years later for unrelated reasons.)
It is (was) moot's website. Other people aren't the ones who set the rules.
Since the design of the site has official topics for each board, you do have to set limits on what's relevant and make new boards when something new comes up. And it's not always possible to make new boards if you don't have mods for them.
In this case, mixing 2D and 3D can be dangerous. It's also a little unfair in that the yaoi board wouldn't be usable for the same thing.
