Reddit is probably the closest thing to a forum.
I guess having a separate domain in a website owned by people rather than one run by a big company allows for a more intimate environment.
Also, mobile which is not ideal for long conversations helped their demise.
Still, I hope they come back big time. I miss them.
Also plenty of good forums had ads. I don't think it's a common thing to want to refuse to click on ads because of high quality content, I would guess the opposite tends to be true.
Anyway, it was easy to come back to a specific topic, so it was easier to find good ones. You could bookmark them, see the number of views/replies or even find them in search engines.
Good content surfaced and survived better, so optimization is probably the wrong word.