Couple other things that haven't been mentioned:
Horford looked old. He's still a useful player, but he's definitely lost some bounce and slowed down a bit. He isn't the Al Horford from a couple years ago.
Rob Williams has no idea how to play with Horford. If you watched Williams play in college, it's very similar to when he had to play with another big then.
Jayson Tatum's indecisiveness as a passer/playmaker is probably the biggest thing holding up the offense. When he's not thinking, he's really good. When he is, he's slow and turns it over a lot.
At one point, Ime had Schroeder, Smart, and Richardson on the floor with one of the Js. I like those guys, and I want to believe they could be reliable shooters, but there is no doubt that opposing teams would rather give them spotup threes with a decent contest than any other action.
On big runs, I just want the guys to put so much effort into defense and trying to be disruptive that they commit fouls. It does stop momentum if the foul is called, and swings momentum if they get a big play.