The examples you mentioned: youtube, and a textbook; are not places to discuss, they are assymmetrical ways to consume information, with little input from the reader's part. Have you ever had a meaningful discussion in youtube comments?
I did not claim that they are forums (useful or otherwise) for discussion. They are good starting sources of information.
There are great places to discuss AI safety out there, but every time they get mentioned on Hacker News they are subject to sneering middlebrow dismissals. That's sort of the OP's point: this is not a great place to discuss or even meta-discuss the subject.