On the one hand I agree with those who are mad at Piolo. Against both Juve and Roma he's changed the formation to be more defensively minded, rather than going head to head with our opponent. Big clubs don't change - especially in a must-win home game. They impose themselves on others. Mancini made the same mistakes in his first spell at Inter (despite having a superior squad) and it held us back - especially in Europe.
On the the hand, what's he supposed to do? We're not yet good enough to outplay Roma, Juve or Napoli. Our defence is rubbish. Roma's three CBs were all superior to ours today, and would all walk into the team (alongside Miranda). He tries to suit the formation to protect our biggest weaknesses (defence, particularly FBs), but that means sacrifice comes from somewhere. Today our formation largely nullified Salah and Dzeko, but we got punished by individual brilliance. Ditto Juve.
It's tough to watch, but Pioli can only work with what he's got.