Everything you ever wanted to know (and more) about light and lenses, explained in a way that's totally comprehensible if you learned electricity and magnetism physics in college.
The problem is that libraries Dewey decimals are managed by librarians who want to sort things correctly. YouTube would be managed by uploaders who wants their stuff to be managed _incorrectly_.
YouTube recommendations and search is a super interesting problem not just because of the scale but also because uploaders are an adverse opponent, trying to keyword stuff their spam.
The obvious solution is to actually have librarians correctly classify the videos. DDS focuses on the nature of the work itself, not on the keywords or spam in the content. Librarians understand how to class all kinds of works, and it should be relatively simple to build a DDS/MDS index (Melville Decimal System since it's open, see https://librarything.com/mds) for YouTube videos. Just like with books, disagreement on classification is inevitable and perfectly natural; there's no perfect classification scheme, though DDS/MDS does a generally good job.
There is already auto captioning done by YouTube. It would be trivial to plug an ai that generates tags and classify each videos based on the whole content.
I am sure they already do that.
Also Jared Owen which does an impressive work of 3D modeling to explain how things and places work. I’m amazed by the level of documentation you have to ingest to model things in such details.
https://www.youtube.com/@animagraffs
https://www.youtube.com/@engineerguyvideo
https://www.youtube.com/@Lesics/videos
The problem is more that they are drowned under the volume of content available.