I don’t think anyone is saying Carl isn’t a great coach.
Clearly, Carl is a tremendous recruiter and salesman (a big part of coaching). He is able to get Age level world champions to follow him to PSU (little extra $ didn’t hurt in his early days to get the ball rolling). Many/most of the world champions are able to maintain/improve on their dominance under his (and assistant coaches) tutelage.
I don’t know that he has proven he can take above average talent and significantly elevate their games to become NCAA champions/world champions, but then again, he doesn’t have to. He starts with world champions. If that one doesn’t maintain their dominance, he moves on to the next world champion at his weight and is able to convince them to go to PSU. It is a skill nobody else has managed to accomplish which makes him a great coach.