We can't have it both ways.
If Retzlaff can audible, the offense gets a lot more dynamic, but we run the risk of bad decisions (repeatedly audibling into the wrong play/making the wrong read).
If Retzlaff can't audible, the offense gets a lot more basic (throw it here or throw the ball away); lower risk and lower reward.
I think the fact of the matter is that AR is a good but not great OC—probably in line with a good MWC team or a middling Big XII team—and that Retzlaff is a limited QB that has wildly outperformed expectations.
Kansas was just a game where both individuals' shortcomings manifested at the same time; AR's conservative, chew clock gameplan left the offense with few opportunities, and Retzlaff repeatedly made bad reads inside the redzone that limited scoring.