I never had any problems with Sarri defense, hes not one of those careless attacking coaches. He was a defensive coach in Empoli. He uses the material he has and let him guide him. But when I say naive and doesnt adapt I don't mean it's too careless defensively, its that his attacking tactic is fairly rudimentary and set in stone, it may look nice, but it's not really effective in big games or moments. You neutralize it and he will rarely throw a tactical trick to mix.
And reality shows that because too many of the big games in either leagues did not work out in his favour at all. It's not a coincidence his record in these games are so worryingly unsuccessful. And we are getting this coach for CL, a competition where the conditions are pretty mixh all games are tense big pressure games? And I'm not supposed to be worried about this hire?
He was naive and too much of a "beautiful football" ideologue at first at Napoli. That defense definitely could've been better and was in the end. He did play a proactive game at Empoli Giampaolo style but being a small club only to a certain degree. He is or becomes aware of the limitations.
Scoring goals/attacking was never an issue at Napoli. It was getting caught during transitions. Same was the case at Chelsea (that and Chelsea players being thick) after early good start (with Jorginho being main culprit) before he changed things around.
He isn't among my top 4 preferences. You can worry about his comments during pressure situations (though much of that would be curbed at Juve, we've rules against moronic complaints) and you can worry about him still being relatively unknown in Euro competitions (alternatives don't really offer guarantees either), but I disagree about judging based on Napoli failures in Europe bc that had more to do with the club.
All we know is that a balanced proactive style favors the competition, and we needed a change (motivation and addressing injuries perhaps being even bigger necessities). And I wouldn't be surprised if Sarri leads to Pep in a couple of years.