Lennon and McCartney had a synergy that made the songs they wrote together better than what either could (normally) do by himself. And they provided unfettered criticism of each other’s contributions, no holds barred. For example, when McCartney came up with ‘World Without Love’, Lennon laughed at the song and mocked it, “Please lock me away...”. The Beatles never recorded it and Paul instead handed it off to Jane Asher’s brother (Peter and Gordon).
On the other side, when Lennon presented ‘Cold Turkey’ as the song he wanted for the next Beatles’ single, the horrified McCartney essentially said, “Are you nuts?” And so Lennon released the song as a solo project.
Exactly, they filtered out the other’s crap.
I believe some of those songs (Cold Turkey) are on the Beatles Anthology?