I think this is a bit of a warped view as this is true for the biggest channels, but the medium and long tail on YouTube has a lot of substance in computer science, engineering, geology, climate science, and much more.

When I was a kid there was Mr Wizard, and then Bill Nye, but it was far more limited than what I watch with my kid.

The land of videos with <1M views is full of gems - and many of the top notch science channels (eg Mark Rober), still give their creators a handsome income. And many of the channels, like Rober, do regularly crack 1M and the recommended list.