I think a big stumbling block is authentication. I think Web 3 could really revive indie forums if the was integrated properly.

It was give people a single sign on for thousands of forums.

I run an internet forum for a very specific topic. I have to manually register people, because before I did that, spammers would come in and crap all over everything. (Fortunately it's not a very popular topic, so I only have to register new accounts a few times each month.) I run the forum on my own dime, no advertising or anything, as a side hobby.

There's also a very active Facebook group. The Facebook group is great for general conversation, but often when a technical question comes up, please just link to the forum where the info is stored. Searching in Facebook is terrible, and what happens if Facebook decides to block access to history for some reason? (Not that they necessarily would, but I've seen it happen many times. Remember when Photobucket blocked access to old pictures unless you had a paid account? We lost a bunch of useful pictures on the forum when that happened.)

They are not disappearing, I still use forums like discogs, XDA, satellite forums, local forums country or city etc. You just have to search and find.

Especially since Reddit passes out bans like candy, it's the biggest forum on the internet and I can't use it because of a site wide ban that I didn't deserve.

You have to go to some pretty toxic plaices if you really want to experience old internet.

Neons.org

I remember when I used to be able to find dedicated message boards for bands that I liked. Now I'm lucky if there's a subreddit where it's just a bunch of people submitting poorly drawn fan art of the band.

Discourse is a great server, i see a lot of places with their own forum now, which is good.