Not all videos have subtitles. I do initially run yt-dlp with the extract subtitles parameter, then I check whether those subtitles were downloaded, then if not, I run whisper.

I'm not sure about whisper, but find YT subtitles pretty poor.

I generally watch videos on 1.5-2x speed (depending on speed of person talking).

I also turn on subtitles in case I miss a word due to the speed, and find it very random at times.

I always thought YT missed a major opportunity: let users submit corrections to the subtitles (probably by clicking on the words it got wrong).

It would have made the experience so much better for everyone who uses subtitles.