But the fact that a big chunk of the user base is there for particular kinds of content inevitably colors all the other communities. This is why the best parts of Reddit are the parts that either restrict themselves from /r/all (or moderate so aggressively that people who show up from /r/all functionally don't post), or are too small/niche to ever show up on it.

They can actually foster an internal community without getting Eternal Septembered once they break a certain size.