The Celtics have to play the Nets like they play the Raptors.
Because the Raptors are so stout in their half court defense, the Celtics switch to an up-tempo offense getting out in transition often; it forces the Raptors to be worried about their transition defense, then the Celtics force them to play against an above average and set half-court defense (which is part of the reason why we've built big leads on them in the past few season).
It's the basis of the style the 2020 Lakers used to run through the NBA in the playoffs. It fatigues the opposing team in the process and requires great conditioning, time management, and depth to avoid succumbing to fatigue themselves.
The Nets are going to score on any defense, to beat them, this team (or any other) is going to have to wear them down by forcing KD, Kyrie, and Harden to constantly get back on defense, dial back our own defensive effort for 3 quarters (to not exhaust our players in the process), and do our best to put up 120+ every night.