I don't know a ton about football schematics or tactics, but it is has always been very easy to see a few things that trend with the Iowa offense, and unfortunately the bad things seem amplified under Brian.
1) An inability to connect vertical passing routes. To my eyes, this has most consistently been the fault of our QBs. Christensen, Vandenberg, Rudock, Stanley and Petras have all struggled with accuracy, and have all had receivers capable of getting separation. This has gotten worse under Brian, as receivers have not been able to create separation under his tutelage (except for Jones) and Spencer Petras is uniquely terrible.
I don't think it's a separation thing of late so much as a "we have a quarterback who can't consistently take advantage of separation" problem. Especially if the separation is occurring with anything past the second read; it's painfully obvious that Petras can't make more than two coverage reads in live action before he either (a) falls back to the checkdown, or (b) has to get out of the pocket, which in the Spencer Petras Experience means "fall over like a dumb fuck and hope you hang on to the ball".
2) The zone run blocking system is ineffective at creating lanes conducive to big gains. 4-5 yard gains are optimal, as Iowa values time of possession to the utmost. This works well when it works, and horribly when it doesn't. This has gotten worse under Brian.
This was a problem in 2017 too when we had a new-ish QB, was somewhat lessened in 2018, and was reasonably non-shitty in 2019 with an experienced QB and 2020 with an experienced RB and line. The common feature is a quarterback you do not fear downfield, which allows a defense to stack the box, bring extra blitzers, and make the OL look like shit no matter what it's doing given that they can't really play those kind of numbers consistently.
3) An overreliance on the tight end in the passing scheme. This, again, is designed to maximize ball security and possession time (and again works well when it works), but minimizes yards-after-the-catch and big plays. It also minimizes options in the red zone and makes Iowa (again!) less likely to score.
Guys like Kittle and Fiedorowicz want a word on this. (One suspects that they got a bit spoiled in 2017 and 2018 and went heavy-handed to TEs, but my strong suspicion is that the last three years is less a result of over-emphasizing TE production and more a result of Petras using the TE as a security blanket because he's incapable of reading defenses quickly enough to get through progressions.
4) Poor offensive line play in general. The elephant in the room. No one wants to criticize the Iowa offensive line, but it consistently lacks cohesion and consistently underachieves. Pass protection has always been an issue under Ferentz, and this has gotten worse under Brian, which leads me to....
You can handwave some of that away by pointing to "youth" and "shitty recruiting in the '18 and '19 classes", and also the problem that a defense that doesn't fear Blonde Forrest Gump at QB is going to be able to overpower any OL at will, but I'm not going to argue the point that the current OL starters are awfully shitty for a program that is built on the development of an OL from underrecruited two-stars to high draft picks.
5) The absolutely boneheaded reluctance to recruit an athletic quarterback. One of the few things that Iowa's receivers consistently do well is...block. One thing the staff consistently has is...athletic tight ends. Both of these strengths are cornerstones to effective scramble drills and yet Iowa completely negates their strengths here. It goes without saying that this has been amplified under Brian.
To some extent, that's true. But even Stanley, nobody's idea of "athletic", had the processing speed to recognize danger, get out of it, and extend a play for positive results. Petras is, in all senses, a tackling dummy. Incapable of recognizing danger, incapable of processing fast enough to evade it.
The problem is that the offense is essentially a giant game of keep away. We keep - you wait. And sometimes it works to the tune of a top-ten team.
But when you can't keep...everything just goes away.
