What's interesting to me is how many people have such long gaps in forum usage. I've pretty regularly used forums for most of my life. Even in the advent of more commercialized social media like Facebook and Twitter. I'd count Reddit (as cursed as it may be) as just another forum/message board though.
A lot of smaller gaming communities have survived or sprung back up as message boards in recent years (examples: Giant Bomb and Waypoint). Then there's always stuff like Something Awful, which is actually where I found a lot of good indie TTRPGs stuff and groups to play with.