The likes of Millsap and Hayward are laughing at this
The coaching staff didn't develop Millsap as much Millsap developed Millsap.
https://appliedsportsscience.com/smart-training-and-hard-work-help-paul-milsap-shine/
I have no evidence that the coaching staff did anything special to develop Hayward, either, and it appears that he started to produce early, suggesting further that the Jazz coaches didn't have much to do with it (although his college coaches might have).
There's no denying that Fesenko could've worked harder, but that can be said for all kinds of players--some who were elite anyway. My underlying point here, though, is the lack of effort and insight that the Jazz coaching staff has made to develop those crucial role players in critical spots (especially the C spot and the 2 spot). Game after game, the coaches tolerated (or ignored) damaging performances by players--Boozer, Okur, Jefferson, sometimes Miles, Derek Fisher (who was probably putting forth top effort) come to mind--and let them stay out there, even when their net contribution to the team was close to zero (or worse). Meanwhile, Fes had his off-court antics (which were damaging to his career, but less of an impact on the team performance) but did not affect the team success when he was on the court (except for not meeting his potential), and yet he was not even rewarded when he did well, much less being given a minimal amount of time to get into rhythm and develop on the court--an essential ingredient that the likes of Millsap and Hayward were granted.
Some players have the self-motivation that lunchpail Jazzfanz crave; others don't come ready made. Of COURSE this conversation would be moot if Fesenko had had better self-discipline, but his was contributing enough on the court to not be relegated to fewer minutes in four years than Greg Ostertag (another notoriously poorly self-motivated player) in one or two. And that's what differentiates Gregg Poppovich from Jerry Sloan (and likely his successor); a case can be made that Rick Carlisle and maybe Tom Thibodeau was able to motivate and unify a team in a way that Ol' Jer never did. I fear that a coach such as Ty with far less experience (and not even the hard-nosed demeanor as a semi-substitute for effective leadership) will be less capable than his predecessor. May TC prove me wrong.
This is about strategy and coaches' ability to be consistent leaders and reward positive performance and minimize poor performance. There doesn't appear to be much analysis by the Jazz coaching staff on matchups and individuals' impact on team success (or lack thereof), even when an interior presence was so lacking; the same thing happened when Fish's "character" wasn't enough to compensate for near-40% shooting and being pwned night after night at the 2 spot. With Jerry, it was coaching by the gut, and that gut never achieved a title, which a more capable coach could've accomplished--as well as developing and disciplining more players that make up a title contender along the way.