I agree, in principle. But I really believe that alot of very average QB's have looked great behind a very good OL and alot of pretty good QB's have failed miserably when they cant setup and throw. This seems to be a secret that Bill Bellichick figured out years ago, he had a statue for a QB (actually 2 in a row), but they could throw and they were accurate if you didnt make them move and gave them 4 seconds to throw. He has always had a very solid OL and also had TE and RB that could help, Brady is truly a great QB, but I am not sure he is the most talented or the toughest or the smartest (well, maybe on that last one, him and Peyton), but he had an offense that was truly designed for him.
I think that Doug Peterson should have a statue outside the football field in Philly just for that reason. He figured out how to use Foles (and Foles got hot) just at the right time and put him in a position to succeed more than about any coach has in a long time. He couldnt do it every time, but he did it once at a very good time.
What is always odd to me is that Chip Kelly also designed an offense for Foles that resulted in one of the best seasons any QB had ever had at that point, and it was completely different. Foles was an odd guy, he excelled in certain situations and was just terrible in others, not many QB's have had the extreme of seasons that he has had.