the problem i have with educational youtube is that it's competence porn. it's quite satisfying to watch lyle peterson, kiwami japan, grandpa amu, nigel braun, grant sanderson, andy george, or xyla foxlin working through the problems involved in creating something, to the point that hours spent getting satisfied that way displace the far more effortful hours required to work through those problems myself. but i don't gain skills by watching someone else work through problems (or, in the less praiseworthy cases, glossing over problems); at best, i might get an idea to try out, or a feeling of inspiration, or a declarative, factual understanding of a particular mechanism—a kind of understanding which still requires exercise to convert into knowhow. but it's much easier to just click on another video and vicariously enjoy someone else's stunning competence than to close the window and struggle with my own
worse, sometimes it isn't actually competence. yesterday i watched a video where a guy made opaque soda-lime glass and convinced himself it was a better refractory than his insulating firebricks because he was, among other things, confused about thermodynamics, confused about different material properties, confused about the composition of waterglass, confused about the composition of garden lime, and confused about the temperature of his oxyhydrogen torch (and, I suspect, in significant danger of blowing his foundry to kingdom come)
watching porn or sex tips videos won't make you a great lover. neither will reading alt.sex.wizards
fifty tom scotts is ten hours a week of, basically, watching porn. i spend more time than that on watching the youtubers listed above and others; what if i spent that time on deliberate practice instead? ten hours a week of etudes might not get you into juillard, but pretty soon you're better than the average garage band member
where do you get your etudes or katas, and how do you judge your success on them? textbooks are pretty okay for that, and it's possible to make youtube videos with exercises in them, but those aren't the videos that become youtube hits. and i think it runs counter to the nature of the medium: not just memetic fitness, but also the effort gradient for both creators and consumers