From the first moment I first went online in 1996, forums were the main place to hang out. In fact the very first thing I did was join an online forum run by the Greek magazine "PC Master" so I could directly to my favourite game reviewers (for me it was Tsourinakis, for those old [...]
Plenty of console Homebrew and general gaming forums are still around. Like GBAtemp and ResetEra.
I think all forms have really been about niche things for the most part. There were some general purpose forms but most of them focused around some Central subject that is core to their identity.
Truly general purpose platforms that attempt to be about everything weren't really a thing until social media, with digg and Reddit.