It’s far easier to grab an “archival” grade copy of a YouTube video (includes thumbnail, subtitles, metadata, etc) and ask the program to embed all the data within the video file itself. It can even remux all videos into a selected container format, which is really nice.

YouTube-dl has gone slow af ,yt-dlp is fork that solves that ,my guess is some kind of fingerprinting YouTube is employing to throttle YouTube dl