It's well established that while Lennon and McCartney co-wrote many of their early songs together "eyeball to eyeball" as Lennon stated in a later interview (I Want to Hold Your Hand was written by both of them while they sat at each end of the same piano, for example), but much of the middle years and most of the late years were written solo and then brought to the rest of the band for improvements. There are many songs credited Lennon/McCartney that were written and performed without the others' input.
DixonHur is also wrong about Lennon's musical talent and song arrangement, saying "it's usually just a piano." It's very trendy to shit on his music these days, but the "Lennon was the lyrics guy while McCartney was the music guy" is an old trope that conveniently ignores complex songs like Strawberry Fields, Happiness is a Warm Gun, Day in the Life, I am the Walrus, Steel and Glass, Whatever Gets You Through the Night, Starting Over....there's a long list. But it is the unpopular opinion thread, so keep it up.