I have used the sentence ‘In general, the doctors weren’t all the much better.’ in an article I’m writing; to me it sounds perfectly well, but to my advisor, it didn’t. Is it grammatically and idiomatically correct, and if so, how can I explain the grammar behind it?
The following idiomatic expression is used to convey a different meaning from what you are probably suggesting. You should probably say...."In general the doctors were not (so) much better"
- used to say that something makes a situation, experience, etc., even better than it was:
- My daughter loves taking care of children. If she can earn money by doing it, so much the better!
(M-W) (Cambridge Dictionary)
Note: in your sentence "better" is an adjective, while in the idiomatic expressions "the better" is a noun.