So I was reading a blog post out there:
https://punkthefrog.bearblog.dev/youtube-apocalypse-and-other-relevant-thoughts/
I've also been thinking about this. yt-dlp is an important tool. But when thinking about what to save, it has really shown that so much of what is on Youtube is very "of the moment" and not really worth saving. I love watching food/travel videos, but I'm almost never watching the same one twice. Even when using YT to plan a big trip, we re-watched a few videos about Prague several times but never again after the trip. What on Youtube would really survive the test of time? It made me think of sports fans, who can't get enough sports, but would never watch last years games because those are over and done.
I've concluded that general educational videos are worthy of hording off of Youtube. Things for my kid to learn as he goes through school, and videos to help him learn another language or culture. Those feel like the things we could download as he grows and have available locally for watching. A setup that allows for that on-demand and without ads would be valuable.
Otherwise, a huge amount of Youtube is really only valuable during the short period it was originally made.