He hasn't won enough games. Simple.
The more specific answer is that he has not evaluated and developed talent well here, and he's also a average-at-best in-game coach. I think ultimately that is why he has not won enough games. Basically, he doesn't do much well outside of recruiting.
The cliches and cheesy phrases don't bother me (they are just funny), and they wouldn't bother anyone if he won more.
Secondary to not winning enough, what also bothers me is that I think he has fairly low expectations for himself and the football program. I think he's satisfied with the job he has done here. He thinks he's gotten the job done, and thinks than an 8-win regular season with no division title being the ceiling of the Tennessee program is sufficient. I think he's really proud of himself for digging Tennessee out of the ditch, which he should be proud of, and he thinks that should absolve him from failing to win a division title in 2015 or 2016.