This is a little weird but when I was in middle school, me and my friends would make our own websites with free site-building tools, and always added a "comments section" (a guest book) to every website we made, and these comments sections became means of a pseudo-social-media. Apparently a lot of people thought that was cool so it became a fad for like a year and a half of just making our own websites and talking through them.
Other than that I frequented Neopets and Newgrounds mostly (I was not yet allowed to have a YouTube account but my parents didn't know what Newgrounds was) until I stumbled upon deviantART and my life went to all hell