https://search.marginalia.nu/ made the interesting observation that a big chunk of that amateur OG internet never stopped or went away, Google etc. just stopped linking to it and it went invisible.
The vast majority of people on the internet are not ever exposed to that kind of web (and most of those who were have moved on). How does someone even find out such a thing exists? How does someone figure out how to participate, if their entire web experience comes from facebook-twitter-youtube-instagram era?
In the 90s, the original amateur internet was something you'd be inevitably exposed to if you did anything at all on the web. Geocities was a thing, ISPs often offered free space for hosting personal home pages. I saw normies, total non-geeks make personal home pages because that's just the kind of thing people found on the web and wanted to try. My older sister had her own homepage. She's not a programmer and not a geek. Her site was a part of some webring, linking other sites made by teenage girls..
"Social media" was forums, likewise hosted by individuals, often in conjunction with their personal home pages, linking to other such sites...
I think the vast majority of it is simply gone.