Vuc just isn't playable in this series.
Tell that to Joe. It's been a glaring issue the entire series. But he still keeps trotting him out there.
The reality is that we don't have anyone on our roster who can defend Embiid in one-on-one coverage. Garza is just the same. And Q can't defend him without fouling (or being called for fouls given how Embiid is a master at embellishing contact).
I think their plan is to have Vuc there as a floor spacer on offense to force Embiid to come out to defend him and open up the lane for drives, and they are living with his defensive deficiencies. They just need to make sure they cash in on the other end.