Come on, our team outside of Lebron sucked last year. Back when we had Kyrie we thrashed them every year.
And the Celtics had...what, exactly? In 2016-17, we were the
defending world champions, and had pretty much that entire squad returning intact. We had indisputably the best player in the world, plus two other All-Stars. They had
one all-star, who admittedly was also Second Team All-NBA. Of course, he barely played because he had a torn hip that required surgery, so they had none. They didn't even belong on the same floor as our guys, and they still managed to win one game
in Cleveland during that series.
In 2017-18, you may have a point, because they'd added Kyrie Irving and Gordon Hayward, who gave them two legitimate...oh wait. Hayward missed the entire season, and Irving missed the entire playoffs. Oops. So they had Al-freaking-Horford as their only All-Star. They had no business even making it to the Conference Finals, except Stevens coached his ass off and got a rookie and a second year guy to play way over their heads. But to you, that Al-Horford led team
underachieved because they only took the Cavs -- who had the best damn player in the world - to
seven games.
In general the Celtics in the playoffs have beaten teams they were supposed to beat, and not pulled off anything surprising.
They beat every single team they played except the LeBron James led Cavaliers - made it to the conference finals both years. The comparative garbage they had in 2016-17 in beating us a game in Cleveland, and especially taking us to seven games last year without Kyrie or Hayward...isn't that overperforming on their talent?