Why do you think that? YouTube has lots of content, some of it excellent, but the vast majority of it is of dubious educational quality with tons of trash and misinformation. Much of the educational content that is worthwhile is also superficial compared to other sites on the internet that have quality and accuracy standards for their content. Some examples include khan academy, coursera, and udemy. I'd even include wikipedia before YouTube.
I think you're both right. It's very dilute, but even so it's many orders of magnitude bigger than the counter-examples you give, and even given the dubious content you have to wade through, the absolute volume of high quality info you can find there is unprecedented. Also it's much lower friction to access (well Wikipedia is about the same, but all the others are gated to varying degrees). So I would contend that YT is uniquely significant as a repository of educational material.
That all being said, I agree with your original point - how they moderate/censor that content is and always has been solely YT's prerogative.
https://en.wikipedia.org/wiki/List_of_most-subscribed_YouTub...
YouTube is mostly about video entertainment.