It's not that he can't coach but rather he has failed to adapt to the changing evolution of the game. You don't beat 1996 uk if you can't coach, you don't take Memphis to a 38 win season if you can't coach, you don't win 38 twice at UK, something no other UK coach or any other coach at any other program has done even once, you don't take a primarily freshmen team to the national title game, etc, if you couldn't ever coach.
The calipari we have now isn't the calipari of even 4 years ago in 2018-2019 though. Something broke in him and the current version isn't a good coach at all.