Actually, I think (not having read Elijah's book, though I've read others, and enjoyed them a lot) that there is a different related point.   I put the shift at the "White Album". You can see by the time of the White Album that the Beatles had not only assimilated all the relevant styles, but were portraying these styles to their mass public one after another ("Happiness is a Warm Gun", "Yer Blues", "Helter Skelter", "Back in the USSR", "Revolution",etc.). -- the White Album is one pastiche after another. There is a movement into irony which is different from the way in which the Beatles had been absorbing previous styles before. I mean, the great thing about the Beatles starting out was the huge absorptive capacity they had, and how it fueled their own innovation. They borrowed from everyone -- but it was done as a way of getting close to the music, that deep thirst they had. "The White Album" is different: the musical form is now something that can be put on or taken off at will. After that, every subsequent movement comes "pre-framed". The most innovative movement after the Beatles was Punk Rock -- and that was deliberately framed as let's "Get Back" to the early R&R. It is as if after The Beatles, nothing comes without quotation marks. So (and again I haven't read Elijah's book) there is something to the notion that they killed naive, pure R&R.

Exactly the same thing happened with Joyce's Ulysses, and Matisse's Bonheur de Vivre.

I think the interesting thing is that by the White Album it is clear that the Beatles had essentially wrung everything out of the tradition into which they were born, and were floundering around, trying to move the whole enterprise. Musically, it is a pity they all went into mutual hell at that moment -- and I have little doubt that this impasse was a big contributor to why they broke up.

yours,

Peter T.