Being a highly lauded author doesn't make you a good teacher either. The best writing teachers are probably relatively nameless individuals out there at various colleges and universities, or maybe even high schools. But no one is going to pay for a "masterclass" from them.

Sorry, that was exactly my point. And to your "no one is going to pay", that's pretty much exactly what The Great Courses Plus subscription is doing - using relatively nameless individuals in academia to do real teaching. People (including me) pay for it.