If things go wrong, blame has to be apportioned between the coach and the sporting director (if we look at it fairly simplistically).
If the squad given to the coach is inadequate, then it is the director's fault.
If the squad doesn't perform to its capabilities, it's the coaches fault.
Juve's team/squad is still the strongest in Italy, so there are limits as to how much blame can be placed on Marotta.
He certainly has to take a share of responsibility for Juve's bad start to the season, though, as he was very late in completing the squad this summer.