You are the same coach regardless of talent, there maybe a difference in the W/L ratio. But you are the same coach. McElwain had elite talent at Alabama, mid major talent at Colorado State, and a mixed bag at UF moving towards high mid major. The talent doesn't effect his ability create strategy, all it does it change the pieces that he is making that strategy with. McElwain was a poor coach in 2015 with better talent, just like he was a poor coach in 2017 with high midmajor talent. The losses of the CC 9 and the injuries (which could be related to his ability as a CEO) didn't change what he was as a coach.
He was more than a poor coach, he was a poor CEO. The S&C was a problem for 3 years, the offensive play-calling was an issue for 3 years. As CEO you have to remove the problems in the system, and he failed to do so. For all of Muschamp's faults, and there were plenty. At least he did try to fix the offensive strategy. I may disagree with the people he chose to fix it with, but at least he tried something. McElwain by the end of his tenure was an absent landlord failing to fix the problems that occurred under his own leadership.