I don't know, the big communities are getting more shitty(=image-boardy) by the day, but smaller and well moderated subreddits are still filled with a lot of expertise and decent people.
You're correct but that won't save them. Advertisers aren't going to spend the money necessary to support the whole structure based on a few smaller subs that are decent.
I was with reddit near the very beginning. What made it special is pretty much gone except for those smaller niche subs and those can be easily destroyed once they come to the attention of the regular reddit rabble. reddit has no system in place to keep those small jewels from being destroyed.
The site will fail. It isn't a matter of if, it's a matter of when.