> They can literally leave school and already be professionally competent. I think we’ll see them leapfrogging millennials on the career ladder because they had a youth where they could spend their entire time learning literally everything there is to know about their passion for free.
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.
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.
Are you sure, that's what the original comment said?
I interpret the quote you posted as "they can already know everything about their passion when they leave school", which would mean that YT is not a replacement for school - but an addition to it.
It's not directly equipping the audience with professional skills for a scientific career, but it is generating interest in science, and indirectly encouraging people to expand their own STEM skills and knowledge. I'm sure that dozens (hundreds? thousnads?) of people have gone into mathematics at least in part due to an interest generated by the likes of numberphile, etc.