Actually, Dave never says in the book that Dylan wasn't a genius, or that Ellington and Bach were. The only person he names as a genius is Rev. Gary Davis.

What Dave believed was that the 1960s folk scene was thrilling and produced some excellent work, but that it was based on some very limiting artistic models, with the result that people like Dylan, brilliant as they were, were not pushed to the full extent of their abilities. They were allowed to get by with a lot of sloppy poetry and three-chord, repetitive melodies that would not have been tolerated in a scene with higher standards. And the result was that they created some superb work, but didn't maintain anything like the consistent level of an Ellington or a Bach.

Dave's favorite writer out of that crop was Joni Mitchell, because he thought she had done her homework and put more effort into polishing both words and music until they were as good as she could make them.

On the whole, he did not think his friends were in the same class with people like Harold Arlen, Cole Porter, Hoagy Carmichael... But that was not because they were less full of "genius." Dave didn't worry about genius or art; what he admired was someone who studied their craft and kept getting more expert at it -- as he did throughout his life. His motto -- one of many, actually -- was "Take care of the craft, and the art will take care of itself."