In case you're wondering, Stevens signed a contract extension prior to the playoffs and will NOT be fired as some fans want. He's had four different teams the past four seasons and had led three of them to the Eastern Conference Finals in years they weren't predicted to get there. There was the Isaiah led team of 2017. There was the young guys in 2018 that made the Finals despite the loss of Kyrie and Hayward for the season. Last year's Kyrie led team obvioulsy failed miserably.
They lost Kyrie, Horford, Rozier, Morris, and Baynes this past summer and really only added Kemba Walker. Then Hayward got hurt for the first two rounds, yet the Celtics still made the ECF. Sure Stevens can improve on some things, and I'm sure he'll start working on them very very soon, but he's not the problem for Boston. And long term his calm demeanor works. Every team doesn't need a screamer like Nick Nurse. Erik Spoelstra is another calm, laid back coach and his teams have had a lot of success.