I think that even if there were a wide array of forum websites, the discussion culture would be very different than the old days. The majority of people's default device now is their phone, and that discourages the kind of longform text posts that were once common. You'd just have a million little Reddits.

And that's not to mention the deleterious effects on discourse of an upvote/downvote functionality, which wasn't part of old forum websites but today's forum software lets you implement it.

It’s not that big a change these forms have existed for a long time, AOL was a giant closed Goliath for a large number of users.