Nah, it's not that simple when it's the last minute and the opposition have centre backs in your own six yard box.
He marked the correct man and he did the same in the move just prior when DDG saved. Bruno was supposed to cover the left back but failed to.
That said, his positioning in general throughout the game was terrible. But generally speaking (as in most of last season) it was very good.
edit:
this is the goal, he has to mark Maupay here otherwise he's free on the penalty spot.
Bailly is tracking the 4, Maguire has someone, and I guess its Lindelof? at the front there marking no one? Furthermore, Fernandes is covering the runner so he should be able to trust his teammate to stick to his man, as the only other option is gamble and leave Maupay free.
As an aside, look at the space the guy has on the edge of the box there too. Rashford just standing there ball watching.