Has the show declined?

I've always wondered that myself, why people are so quick to place blame or greatness on a writer when their name is attached to a particular episode, when the reality is that most of the episodes are written in staff meetings by large groups. I might be wrong, but I was under the impression that the credited writer was usually the one who came up with the basic story but that the whole staff would flesh it out and put in most of the jokes in a collaborative manner.