> There are way too many 15 minute videos along the lines of "How to do X in Y" which should be 30 seconds long.

This is why I stopped using YouTube a few years ago and heavily prefer text+image tutorials to videos nowadays. YouTube is pushing longer videos, because they show you more ads in the middle of them and creators are also rewarded with more money for longer videos + they can insert their "sponsor messages" a.k.a. even more ads.