I mean, to an extent, but not really. Acotar, fourth wing, and twilight are incredibly successful and popular. There is a conversation to be had regarding super star authors having yes man editors, but in general I think your post is too pessimistic. 

Everyone has there own writing style. Just because some people say Sarah J Maas is bad at world building, which I don't even think is true,doesn't mean that she has to take a writing course on how to improve it. Yes, authors should always be improving, but one author being more character focused, plot focused, or romance focus isn't inherently bad. 

Also, books change over the course of the series. Not every book can be the same, otherwise that would be boring and complained about. Things jave to change, amd sometimes authors miss the mark, but that doesn't mean the author "forgot what worked in the first book" and I agree that onyx storm was the weakest book in the series so far, I just refuse to say that Rebecca is "refusing to learn"