This isn't necessarily true. Here are some statistics taken from the Hummingbird categories page, I'd assume these are the average threads created per week.
5 gaming, 32 anime, 12 general, 28 misc. Per week.
Assuming most threads with shitposts are moved to misc, there are still threads avaliable which promote discussion.
If by stale, you mean "less fun", well that is a subjective enjoyment which you shouldn't push onto others.