I think that you are right that Herman maintained the musical tradition that was more the 50s and 60s. The Sondheim and Kander built on that in the 70s and 80s, altering the tradition in unexpected ways and becoming Broadways kings. Unfortunately in my eyes then came those men who seem to write musicals that had one or two decent songs to them. Many became movie musicals. Oh well, I am getting old and will always see Sondheim as my god. (I'm not saying he did not produce a disaster or two - have you seen Assassins?)