So what is Mike McCarthy missing that he could acquire to make himself a better coach, as he is an already very good one?

The ability to adjust on the fly: https://fivethirtyeight.com/features...cid=538twitter

FiveThirtyEight @FiveThirtyEight
Instead of forcing Foles to play like Wentz, Philly changed what it asked of its QB and receivers.

McCarthy did do some of this with Hundley, there were a lot of WR screens, but when dropping back it looked like TD then check down but with a QB who could not buy time effectively.