Those forums exist and are more widely-used than ever. They're just mostly hosted on reddit now.
Personally, I have found myself resorting to discussion sites focused on a single topic, like Hacker News instead of /r/programming, or DharmaWheel.net instead of /r/Buddhism.
The only thing that the administrators outside your community do is the shitty redesigns of the UI (big thanks to them for the "old.reddit.com" option though).
Everything else is done by the community of a subreddit.
It is far and away worse than fph and incels in terms of content, but for some mystical reason that's totally not /u/spez vetoing any attempt to reign it in due to his conservative ideology, it has missed the banhammer.
Complete political whims.
Every subreddit is constantly in the process of eternal September, which kills the dynamics of getting to know one another that were common on forums.
Social media that is good cannot have advertising and cannot be an algorithmic Skinner box that maximizes engagement.
I am starting to think of competing with Facebook as creating online tribes that are costly, perhaps even financially very costly, but full of rich directed action. Sometimes like the dynamics of a church, where users are collated into tribes of limited size.
Can't you just sort by new...?
Well, that's the double-edged sword of reddit: it helps niche forums stay alive by constantly bringing in new users that originally visited reddit for other reasons. But that visibility can also kill them.
Still, aren't there lots of private subreddits or subreddits where only subscribers can post? If mods are active and ban regularly, you can preserve a culture if you want.
As of March 2019 Reddit seems still quirky and interesting though...
This can be read as a searing indictment of reddit: it's quirky and interesting, but its value ends there. There's no real discussion to be had and most topic-specific subs are wildly uninformed for most of the things I have any personal experience with. This is certainly not limited to the tiny slice of the world I know well.
Let's take some of the DIY forums. Reddit can get pretty useful, but how does this relate to 1999? Back then, getting DIY videos was difficult. Now the trick is getting to the right kind of quality videos. But perhaps in 1999 if you read something and engaged online the experience was maybe more personal/fulfilling/substancial?