Beatles producer George Martin worked with the band extensively on each of their albums. He got to know the band and their working style well as they grew as artists. While he was typically happy to see their growth, he said they began taking too many creative liberties beginning with one album. He shared why this became a problem for the group.
George Martin said The Beatles lost focus on one album
In 1967, The Beatles pushed the limits of what was possible with an album when they released Sgt. Pepper’s Lonely Hearts Club Band. They continued to push boundaries with their later albums, which Martin viewed as a problem.
“During Magical Mystery Tour I became conscious that the freedom that we’d achieved in Pepper was getting a little bit over the top, and they weren’t really exerting enough mental discipline in a lot of the recordings,” Martin said in The Beatles Anthology.
Source: imdb.com