No one said he didnt make mistakes dont strawman the point. There is a huge difference between saying he did great but made some mistakes, and saying he is stubborn and tactically clueless.
He Played 4-3-3 against Madrid with marchisio as winger. A formation that we cant have as our main one even today with our huge squad, not when we had $#@!ing giovinco and pepe.
Switched to 4-3-3 midgame against Galatasaray. Used 4-3-3 countless times in his first season. Developed the 3-5-2 for Juve because it best fit the squad he had and to this day we are still using it.
He didn't change at Chelsea, he is doing the same thing he was doing at Juve. He tinkers with a bunch of formations until he finds the formula that fits the squad the best. The one he seems to finally rest on is usually a weird invention of his. Thats tactical brilliance especially if he does it twice. That is not to mention how much he improved Italy. Tactically Clueless coach