There was a stain on the program when it came to developing quarterbacks for the most part, and a good chunk of this failure to develop QB's was all but self-inflicted.
From 2010 through 2014, Charley Molnar and Chuck Martin were hardly the epitome of a QB coach who could make things happen. Even when Everett Golson turned in a very good 1st half of 2014, he all but disappeared in the 2nd half, and Martin couldn't get him to find his mojo again.
From 2015 through 2016, Mike Sanford had the most successful run as a QB coach, since Malik Zaire had shown some promise in 2015 until the injury, and Deshone Kizer flourished. I would argue that Kizer did an even more impressive job in 2016, given how he didn't have a developed WR1 at his disposal, and the WR corps was depleted after numerous injuries (thank you, Paul Longo, for your ineptitude).
In 2017, Brandon Wimbush regressed during the season. I really thought that he had taken that next big step after a good showing during the Michigan State game, but after that, he couldn't even complete over half his passes for the rest of the year (except against NC State, where he went 10-19). He started missing easy short soft tosses, and even throwing it 2 feet above the reach of Alize Mack (who is 6' 4", and has very long arms and jumping abilities) on a 5 yard swingout pass.
More often than not, a good QB coach would have found a way to snap someone out of that funk, but he only got worse in the accuracy and route reading areas.
While folks will rightfully point out that Ian Book became one of the most successful quarterbacks at ND during the tenure of Tommy Rees as the QB coach, Ian Book basically coached himself. If anything, he did his best work when allowed to improvise and be a creative gunslinger.
For 2021, I also won't give him credit for Jack Coan's success, simply because Coan was a polished 5th year veteran who made things happen, despite Rees. If anything, that Fiesta Bowl, where we were overly dependent on Coan's arm (42 yards of rushing against a weaker defense), showed the limitations of what Rees could do without Brian Kelly as a puppeteer.
The Buchner / Pyne situation in 2022 was a disaster. While Drew Pyne turned in some respectable numbers, any other QB with a reasonably accurate arm would have turned in All-American numbers, especially with having Mike Mayer there. For some reason, Tommy Rees couldn't teach Drew Pyne to look over the middle or the left, and that we were only using the right side of the field on most passing plays. It was supposed to be a "spread" offense, not a "narrowing" offense.
I would dare say, that if Mike Mayer weren't there in 2022, we would have had 3 more losses.
As a QB coach, how can you not impart that kind of a lesson on your QB? Yes, Drew Pyne has a weak arm that was basically a step or two better than Tommy Rees' noodle arm, but even then, he would flat-out ignore Styles or Lenzy streaking over the middle, wide open, and instead make a contested throw to Mike Mayer.
So far, we've only seen one season with Gino Guidugli at the helm as the QB coach here, but he did develop Desmond Ridder at Cincy. Being able to develop a 2 star athlete into a 1st round draft pick says a lot about him, and he did it in a controlled, gradual way that allowed Ridder to learn without being overwhelmed. QB recruits take notice at this, and can see that he knows how to develop a QB.