I'm a technically proficient user that's written custom bash scripts for youtube-dl combined with ffmpeg to download videos locally and I still use the official Youtube desktop web browser UI every day for several reasons:
+ transcripts and close-captioning (use Ctrl+F search for text to find the section of video that starts talking about the topic I'm interested in)
+ many videos have index of chapters (deep links), table-of-contents
+ viewers' comments (especially valuable for crowdsourced feedback on DIY videos to point out extra tips, or flaws, etc)
+ external links mentioned (Amazon links to products is especially valuable for DIY tutorials)
+ convenient hot links to related videos (part 2, part 3, etc). Not every creator makes "playlists"
+ Youtube web UI has superfast video scrubbing of the timeline. A local video player like VLC scrubbing of the timeline is very slow compared to Youtube because the youtube backend pre-analyzes the entire video and generates a bunch of timeline thumbnails at multiple intervals. This makes the Youtube web UI timeline scrubbing very fluid with responsive visual feedback.
I like downloading with yt-dlp but I also lose a lot of functionality when I watch videos in VLC instead of the Youtube desktop webbrowser UI. The above points are not relevant to the terrible Youtube app on mobile and tablets.