We could be here all day arguing about what a genius is.
I agree Lennon was in his hey day (63 to 67, with another little flash in the early 70’s) like Mozart etc an exceptionally good songwriter. Probably one of the greatest of his day. So in his field, on a good day, yes he was a genius at writing songs. If that’s what people actually mean, then good and fair enough.
But I do think many people, when calling him a genius, believe that he transcended that, that he was more on a par with “great mind” genius (if you get my drift), which I think is pretty unconvincing.
In the context of the world and human endeavour, “changing the face” of popular western music (an accolade quite a few artists, producers and Simon Cowells could lay claim to) is hardly E=MC2.
And another point I like to labour – John and Paul didn’t invent pyschedelia or “concept” albums – they just did them remarkably better than everyone else, and because of the fame afforded to them by Beatlemania were able to popularise them as ideas.. Their genius (damn) was to be able to take ideas bubbling away at the fringe of popular music and turn them into (exceptionally good) products for the masses.
And for the record, I think it’s pretty hard in any human endeavour (music included) to say “this person invented this idea.” Generally it’s the culmination of many little ideas, with one person (Darwin, Einstein, Picasso, Lennon) being the one to have the fortune or skill to popularise them. History loves a hero. Maybe that is genius. Damn again