The most active online community I ever participated in was actually a mid-1990s BBS. You had to dial or telnet in as I recall. I don’t think membership was open to the public, someone had to invite you.
The forums were all ASCII, no graphics. Navigating around took a while to really grasp—big learning curve for newbies—with all kinds of commands to master. The membership also had a lot of hyperdeveloped customs and ground rules that you could get tripped up by.
Despite all that, it was crazy how much activity there was. There were many subforums, each with a (sometimes tyrannical) mod, covering all kinds of topics from food to religion to politics to local NYC stuff.
Because there was no social media per se yet, this was the main or only such outlet for many users, and people were on it *all the time.* It had a very opinionated and argumentative atmosphere and that seemed to just drive more traffic.
When I left the City I gave up my membership. I guess it fell apart in the early 2000s, but still exists in some greatly diminished, web-based form. It’s crazy to think how much of the tech skills I mastered to use it I’ve totally lost.