This word "genius" is the problem. Obviously Dave Van Ronk could see Dylan's limitations as well as his sources and influences. On Dylan's side, he has produced a very large body of work, which many of us see as stunningly original. That is as a new type of songwriter though, because he penned popular songs which were more subtle and textured than anything which had preceded them. If you don't like him, he comes over as a pretentious show off.
Woody Guthrie had a lifestyle and an idealistic commitment, which made him exemplary in the eyes of many. His songs were much simpler than Dylan's and I see them as being far less ambitious. I felt quite up to writing a dissertation about Guthrie (which I admit was nothing special). However, I would not even have attempted to write about Dylan. You would have to know a whole lot about a whole lot of subjects to write anything about Dylan which was not superficial.
I don't really think that folk music lends itself to producing a genius. It is a field of human activity which tends to focus on participation and taking the best of many rather than picking out just a few of the best.