Kirk Ferentz's philosophy can and does work, but it hinges on three things:
Firstly, a stout defense that forces turnovers, is all but impenetrable in the red zone and under no circumstances lets up big plays.
Secondly, an offense that takes advantage of short fields, doesn't have backwards plays and under no circumstances turns the ball over.
Finally, extremely strong special teams that don't leave points on the field and essentially fortify the field position game that the offense and defense are intent on winning.
The defense depends on the offense to not put it in bad situations. The offense depends on the defense to give them short fields. Both squads depend on the special teams for the same reasons.
If one of those tenets of the system is off, the entire system is going to be off.
It's easy to blame the problems that the Iowa Hawkeyes have on an under-producing offense, but you have to consider the entire team dynamic. Ferentz will occasionally sacrifice points to make sure his defense isn't put on a short field.
The numbers the defense has put up over the past 10 years probably would not have been as impressive if the offense had been more aggressive.
Some people have problems with that philosophy. I respect their viewpoint, but I don't think I can convince those people otherwise, so I won't try.
In effect, any comments or criticisms I have of Ferentz will be strictly within the realm of the system he does run, as opposed to a system he will never run.