I think the biggest problem with Miles is that it's like he's coaching in a daze. When you watch his post-game conferences, it's like listening to a guy in a fog. Team has been playing the same way. One of the biggest issues everyone has with Miles is that the offensive problems have been apparent for years and he seems unwilling to change his philosophy. The Alabama game was a showcase of that when they kept running Fournette up the gut until about 5 minutes left in the game, which is where he got most of his yardage. It's like they have a plan, and if that doesn't work, well then I guess the game is just a loss. Really weird.
The parallels can be drawn between Miles and Tuberville. Except in Tuberville's case, he was actually ahead of the curve trying to implement the spread. He was ahead of everyone. It's just 2008 was a really weird season and he picked the wrong coordinator who in turn went after the wrong personnel. Alabama's 2008 recruiting class was a monster, and nobody expected them to do as well as they did. I think Tuberville was caught off guard in that aspect in recruiting as well. But that was a time where Alabama and Auburn were signing half of their classes from Alabama. Now, each team is only pulling 5-7 guys from Alabama each year. Auburn had a knee-jerk reaction and got rid of a guy that would have had Auburn stable by 2010 IMO.
Les on the other hand doesn't understand that the days of 3 yards and a cloud of dust are pretty much over. Yeah, you can still do it to an extent, but you have to mix a lot of other stuff in there as well. Years ago, Alabama, Auburn or LSU could pretty much tell a defense "Hey, we're running in this gap. Fuck you." and it worked. There is more parity in the SEC west now, and you just can't do that anymore. He has refused to modernize whereas even someone as much of an asshole as Saban has realized he had to change the way he does things.
TL;DR: Les has been successfull overall, but hasn't done shit since 2011 and things are getting worse. He is too stubborn to change his ways, so there seems to be no hope on improvement.