Louisiana is one of the most talent-rich states in the country and the vast majority of the kids there grow up dreaming of playing for LSU, as they're the only major program in the state. They're like USC or Texas in that they should never have a problem getting tons of talent. You're virtually guaranteed to have one of the 10 most talented rosters in the country and with that much talent, winning 75% of your games should be a given.
What separates the adequate coaches from the great ones is whether you can consistently win against similar or greater talent. Over the last 4 years, Les has failed miserably in this area. Bama has dominated him, and he's only winning about 50% of the time against teams with slightly less talent such as Auburn, Ole Miss, aTm and Arkansas. He's 1-9 the past 4 years when LSU is an underdog, and they've never been a huge underdog.
He's put a lot of players into the NFL, but given the talent at LSU, anything else would be surprising. Given the amount of talented players coming out of the program, where are the SEC or national titles in recent years? If I take a Ferrari 488 GTB to the track and run all over the Mustangs, Chargers, and Camaros, does that make me a great driver? No, it just means I have a car that anyone could beat those other cars with. See what I do against Lambos, Porsche's, McLarens and other Ferraris and then you'll have an idea of whether I'm a good driver or not.
In other words, over the past 4 years, Miles has won with talent, not coaching. Any decent coach could do what he's done with that much talent. He's failed to get the talent he has to dominate anyone other than over-matched teams and win titles. He beats the weak teams, struggles against good teams, and gets obliterated against more talented teams. His coaching has been mediocre at best since the 2011 season, and he's shown no sign of being able to right the ship and do anything more than that.