I absolutely agree Groce has probably improved in many ways as a coach. But the idea that he was a good x's and o's coach during his tenure at Illinois has been repeated a number of times and is entirely a reflection of common criticisms against our current coach. The perception of Groce during his tenure was absolutely not that he was a good x's and o's coach.
This isn't the be-all, end-all of "X's and O's" of course (the colloquial division of college coaching into exactly two jobs, X's and O's and recruiting was always pretty much just nonsense), but I think it's reflective of the problems of Groce's time here:
KenPom Offensive Efficiency:
[Groce hired]
2012-13: 46th
2013-14: 146th
2014-15: 91st
2015-16: 142nd
2016-17: 123rd
[Underwood hired]
2017-18: 86th
2018-19: 83rd
2019-20: 38th
2020-21: 8th
2021-22: 30th
2022-23: 68th
2023-24: 3rd
2024-25: 15th
The lack of a star lead guard to initiate offense didn't help, but there were some very good scorers on those Groce teams and for his entire tenure we just did not get them into positions where the game could be easy for them, every last bucket was a struggle, even during a period when the Big Ten was opening up offense-wise. All the best coaches of that era jammed us up with ease.
And then even with bad teams and overmatched players, with overall tactics that led those first two Underwood teams to be the most dunked-on basketball teams I've ever seen in my life, there was an immediate drumbeat of little set plays and out of bounds plays and ideas to get easy buckets, things that fit our players strengths and broke down opponents.
It's a much less system-development focused sport now and a lot of years later, and Groce's success at Akron is very impressive, I'm sure he views himself as someone that has learned new tricks and I'm sure he's right to some extent. But he was a disaster of an "X's and O's" coach here, a sore thumb in the conference, and if I were a major conference AD I would look at his resume with considerable skepticism.
