You know what every one of those things says in common? every generation between when it was created and now has decided it was important and made effort to preserve it. We have no clue or maybe only slight clues of what was lost because at some point some generation decided it wasn't worth preserving. Sometimes it was a hard decision for that generation when they realized they couldn't preserve everything, other times it was not cared about at all. Either way though, it was lost for all time because the chain of caring enough to preserve it was lost.

The data isn’t the valuable aspect of those examples. The metadata is!

We have a bunch of family photos that were preserved for a few generations. It sucks, many of them we know who they are, the most are lost to time and the death of memory.

Pictures without the context are just images of dead people. With the story, they are priceless memories.

Every single thing you cite has been, and will be, copied many times over and preserved that way. e.g. - We don't have the original Bible, we have eleventy-billion copies of it.

I don't disagree that a few things that happen today will be of consequence. I disagree that any single source of that data needs to last for a thousand years in isolation.

There are, I'm sure, one or two examples of thousand+ year old primary sources revealing otherwise lost information that was still relevant in some way. I suspect not many, other than as datum for academics to ponder.

Important information has always survived by copying.