> I don't think this is an apt analogy either because it still suggests that something was lost

Here we disagree and you are wrong ;-)

Of all the old forum lore most of it is lost for the overwhelming majority of internet users.

Some copies exist on old drives here and there, some exist in the internet archive but nothing has been migrated to newer platforms.

Mailing lists were for a long time conserved by Google but forums just disappeared.

I mean, of course "something" was lost? But...things were lost all of the time at the height of the old internet as well. No tech change needed. Communities would rise and fall, maintainers would move on and stop making things available, etc. It seems to me That is just how things change over time.

Like...if IRC was still the height of community, many of the IRC communities that were the most popular in 1998 would still be dead and gone now. Their archives would probably still be lost (it's not like we were better at archiving then). Like for any particular community that you can look back on and see people moving away from it into something else, I suspect people would still have moved away - they just would have moved away to a new IRC instead of...twitter or github or discord or whatever.

It just seems, to me, that people see normal cyclical community transition and blame the fact that it happened at a time when new kinds of communities were rising. I am not convinced that the two have much to do with each other.

There's a reasonable argument that we're actually in a golden age of forums. Subreddits have allowed many more niche communities than before and even traditional style forums have prospered in plenty of cases. There is definitely migration to newer platforms like Discourse and others.

If you think about it with an archivist mindset there are definitely plenty that was lost to time. But that will happen just from natural churn, even if the total is still healthy. And in this case as far as I can tell it is healthy. People talk about all kinds of things in hosted forums of various kinds. I'd be very surprised if the total forum traffic on the internet hasn't been on a steady rise forever, it just rises slower than the total.