I think Joe is aight, but let's be honest, due to the Udoka situation, he was given an already great team, so I don't believe them winning a championship has more to do with him than it does with the team being great itself in terms of talent.
I'm not a fan of his coaching style. The Celtics offense is nothing but the 3-ball, and it's kinda disgusting to watch, especially when they're down in games. I remember during a regular season game at home against OKC, they were down big, and literally every possession up the court was them shooting 3's just to get them back in the game, which it did but it was awful to watch.
Those Warriors and Rocket teams of the mid-late 2010s had much more variety in their offense that even when the 3 wasn't working they found other ways to win. Boston's offense is very redundant and predictable; when the shots aren't falling, they're very beatable, hence why the Knicks won the series because overall, they played better, and the offense was more varied.