YouTube's search experience became so bad that I can't find videos that I watched 10 years or more ago. And I can't tell whether it's because their search algorithm & UI went downhill or because the videos have been removed.
The search feature also seems to return less in general, and has become geared towards suggesting content below the fold. You can get it to keep returning more that's related to the search query by just continuing to scroll, but it runs out remarkably quickly.
So yeah, if you like it, download it. I don't care what anyone says about copyright. Unless it's something you know will be around, it can disappear for good.
I'd love a multi-billion line spreadsheet that just contains videoIDs, titles, channel names, and descriptions from all of YouTube.