I'd say it might actually be 60-40 in terms of responsibility (60% fault for shit players, 40% for a shit coach).
Maybe even 70-30.
This team is absolute shit, make no mistake about it. Specially at midfield. And when you have no creativity in the midfield, maybe playing the ugly 3-5-2 isn't the worst option.
This doesn't mean Allegri isn't shit. It just means that the players are so shit, that even with a coach with decent mentality they would probably keep playing like shit. Like with Pirlo, when they were aggressive and tried hard, but were still shit, specially with those hipster tactics.
But I have to admit I dont watch games anymore.. it's just a wild guess. THAT I can say is Alllegri's fault, for sure. Too many years on this mentality. Problem is, when a normal coach assumes the team in the future, I'm not sure people will have the will to go back to watching it. It's completely ingrained in Juve's DNA. Anyway, Allegri is not going anywhere at least in the next couple of years, I'd bet.
Again: management isn't worried about football performances (they are about results, with low expectations though), or about what fans think. It's their biggest mistake. They're slowly killing the club.