I'm not sure when exactly scene.org was started, and I experienced the demoscene in the late 90s / early 00s, so a different time than you, but I felt there was quite some effort at archiving.
Most demoscene artifacts worth archiving are of course the demos itself, and most of them are published at parties. And pretty much every party of any relevance, including many small ones, pushed their releases on ftp.scene.org.
Furthermore there's the "got papers?" project that archives stuff like flyers around demoscene (and related scenes) events:
https://gotpapers.scene.org/
http://scene.org kinda grew out later in the 90s but I think they took in all the http://hornet.org archives that were the go-to ones before scene.org kinda took over to keep them preserved.
While scene.org has been a solid destination for the past 20 years for more "modern" platforms there has also been hard work in trying to preserve the C64 scene information that in many parts predated scene.org , this can be found on http://csdb.dk
Most demoscene artifacts worth archiving are of course the demos itself, and most of them are published at parties. And pretty much every party of any relevance, including many small ones, pushed their releases on ftp.scene.org.
Furthermore there's the "got papers?" project that archives stuff like flyers around demoscene (and related scenes) events: https://gotpapers.scene.org/