Goff played great in a great offensive system with great player around him.
Was McVay a big improvement over Fishers offense? You bet a huge improvement.
Was the QB coaching under McVay better than under Fisher? Yes tremendous improvement.
Did Goff step up and do a great Job? Yes he he did a great job and improved by a huge amount.
Lets face it Tom Brady would not have done well under Fisher so McVay should get a bunch of credit.
However, Goff took his game to a whole new level and is now one of the top QB in the League.
I don't see anyone saying the Tom Brady is only good because of Josh McDaniel. You need a good QB, good surrounding cast, good coaching and a great offensive system. Praise God that the Rams have all of these components.