I think it was the interview by Tom Snyder on “Tomorrow”, but anyway, he said, “we weren’t a very good group.” (iow, not “band” but “group”)
Interestingly, Lennon often criticized the Beatles after they broke up, but would staunchly defend them against outside critics. It was sort of the "I can make fun of my little brother, but you can't" mentality. I think he always felt like he had sold out, which (along with prolific drug use) is a reason he became so weird later. Being a member of the most successful and influential group ever apparently was not good enough for him.