If Bronco took BYU to the CFP and lost, I suspect nearly all of the criticisms would cease (unless he lost that game because he used two timeouts to ice the kicker on a PAT).
The criticisms of Bronco are BECAUSE he has shown no indication of being able to lead BYU to a BCS/NY6/CFP bowl game. He's been here what, 10 years, and had many seasons with schedules favorable to get BYU in one of those bowl games. And he hasn't delivered. It's that simple.
I think Bronco is a great man, and I feel bad for some of the hate thrown at him. But unfortunately I think there are many valid reasons for most of the criticisms.