The reason this team struggles with consistency is that they are a bunch of DUMB basketball players.
They get reckless on offense, force things all the time which results in turnovers, they take bad shots, go 1-on-1 way too much, they don't move and the ball doesn't move, very little playmaking, really bad passing team and a mediocre shooting team that just keeps jacking 3's when they are cold.
Then there is defense, they lose sight of the guy they are guarding off-ball, they lunge at fakes, they do not rotate correctly to cover the weak side, they don't box out, sometimes they wander around lost guarding nobody, marcus smart screws up and yells at his teammates.
Tonite is a great example. Celts are playing hard, hustling, shooting the 3's well, but getting lost on defense and losing control on offense which has resulted in missed shots 10' and in or turnovers.
Very painful to watch when you care about the team.