Not so sure you can lay all the blame at Brian's feet for Iowa's bad offensive.
The coaches recruit. After a horrible year offensively in 2021, when Iowa ranked circa 122nd in total offense, rather than fire Brian Ferentz, they double down on him, and name Brian Ferentz as QBs coach, in addition to offensive coordinator. He ws an o-lineman as a player.
In 2022, the offense is 130th in total offense out of 131. The highest rated recruit ever committed to Iowa football, an O-Lineman, decommits in Dec. 2022 because he didn't want to settle - while young people can change their minds, having the 2nd worst offense in football, and doing nothing to change the dynamic with the coaching staff is on Brian Ferentz for not resigning as offensive coordinator, on Kirk Ferentz for not demoting or terminating Brian, and the Iowa Athletic Director Gary Barta, for not terminating Brian after 2021, or in 2022. Iowa's recruitment of offensive players suffered in 2022, and that will affect 2023, and beyond.
The O-Line and quarterback positions were extremely weak. You work with what you have. Iowa had an immobile QB. Instead of moving him around with sprint back passing, and rollout passing, they leave him in the same spot in a collapsing pocket almost every pass play - the spot where D-Lineman are teeing off to sack him. Petras could not scramble from a pocket because he has bad feet, but he demonstrated he could throw on the run on the few occasions he rolled out. Brian rarely rolled him out; I didn't see one play where they used him to sprint back right or left, and throw. Brian didn't work with the foibles of the players he had to make the offense better. He is not a good O-Coordinator, a very bad QB coach; and not a good tactician.