They all brought something unique. Chapman brought the legit leading man good looks and acting chops. Cleese and Palin brought the slapstick and comedic timing. Jones and Gilliam brought the writing and “behind the scenes” mastery. Idle brought the music.
Idle could have been a legit Grammy mainstay with his music skills. The score of the group was, imho, the most iconic thing they brought. Every Sperm is Useful, the Lumberjack Song, Always Look on the Bright Side of Life, Camalot…. Legit classics, all.