Yeah, basically every 15 minute YouTube video, because the amount of actual content I care about is usually 1-2 sentences, and usually ends up being the first sentence of an LLM summary of the transcript.
If something has actual substance I'll watch the whole thing, but that's maybe 10% of videos I find in experience.
I'd wager there's 95% of the benefit for 0.1% of the CPU cycles just by having a "search transcript for term" feature, since in most of those cases I've already got a clear agenda for what kind of information I'm seeking.
Many years ago I make a little proof-of-concept for displaying the transcript (closed captions) of a YouTube video as text, and highlighting a word would navigate to that timestamp and vice-versa. Such a thing might be valuable as a browser extension, now that I think of it.
YouTube already supports that natively these days, although it's kind of hidden (and knowing Google, it might very well randomly disappear one day). Open the description of the video, scroll down and click "show transcript".
Searching the transcript has the problem of missing synonyms. This can be solved by the one undeniably useful type of AI: embedding vector search. Embeddings for each line of the transcript can be calculated in advance and compared with the embeddings of the user's search. These models need only a few hundred million parameters for good results.
One of the best features of SponsorBlock is crowd sourced timestamps for the meat of the video. Skip right over 20 minutes of rambling to see the cool thing in the thumbnail.
If something has actual substance I'll watch the whole thing, but that's maybe 10% of videos I find in experience.