Boston, like every other team in the league, is trying to be like Golden State. The Celtics should instead be their own team.
A big problem with the NBA is that it's a copycat league. Once Miami started winning with LeBron at the helm, other teams started trying to win with "small ball"—forgetting, of course, the small fact that Miami had LeBron.
The Warriors, of course, didn't (and still don't) have LeBron, but they had (and still have) the two best 3pt shooters in the league, so they tweaked the "small ball" approach in a very effective way—taking (and making) tons of threes. And then they added the league's second-best player to their roster, and he's a pretty good 3pt shooter too. Now everyone's trying to mimic the Warriors—forgetting, of course, the small fact that no other team has Curry, Thompson, and Durant.
The Celtics don't have LeBron. They also don't have Curry, Thompson, and Durant. The Celtics do have some very good players, but not those players. They need to find a way of playing that maximizes their players' strengths, as opposed to trying to make these players become the Warriors.