Hi HN,
I watch A LOT of educational YouTube videos but wasn't forgetting a good chunk of the details because I was only really passively watching. So I made a tool that generates quiz questions/flashcards from YouTube videos, and uses spaced repetition like Anki or Duolingo to keep it in memory.
Let me know if you find it cool/useful (or terrible ) or if you want to know a bit about the details!
I know you've addressed the video selection in the playlists, but I would highly suggest doing something to get it to differentiate "educational entertainment" videos (I notice a lot of Real Engineering and Economics Explained and CGP Grey videos) and actual education videos: primary-source explainers from teachers and subject-matter experts. The information density in the latter is way higher, and I think people overestimate the educational value of the former.