School isn't a panacea either. I think I've done above average in school for the most part, but I never learned enough to have "professionally applicable skills". And the skills I actually use in my profession I learned outside of school.
The thing is, when people are motivated to do something, they'll learn what they need. Otherwise, not even school can force feed students into learning those things.
Now if a kid watching videos that are long form treatments on specific subjects and are following allong with a pen and paper doing practice problems, sure, thats a case where youtube might give you some serious skills, but that is a tiny fraction of kids and those same kids would have been doing the same shit with textbooks at their local library. Youtube is waaaaaaaay closer to being purely a distraction than to being something we could consider "educational" in any serious sense.