The effort on defense is pathetic.
By the same token, the Spurs execution is excellent.
It's much easier to execute when you are wide open or have tons of room.
And their pick and roll and pick and pop game is impeccable, they have hit many contested runners, and some outlandishly long threes.
Celtics defense has not been good but, give the Spurs credit, their offensive system is creating as many good looks as poor defense has and they have made the shots.