For one, some of those left-it-better-than-found-it dynamics are:
A) driven by forces above Kelly and/or decisions made in spite of Kelly (firing his S&C coach, improving his staff by going with younger, non-family members, investments in facilities and nutrition, etc.).
B) in the relative context of a horseshit list of coaches preceding him.
And, second, the description fits a "bridge" coach - someone that gets you out of the desert but not to the goal (championships). And I struggle to think that should be considered success when it is a 14-year term.