Yeah, I would not call IT a ball stopper or even a ball dominant PG. I mean, the latter is something he's been on the Celtics, but a lot of that is the lack of another scoring option.Not sure I agree with the blanket statement that he's a ball stopper. He was the only creator they had last year, but his kick out passes showed advanced vision in my opinion. It just doesn't make a ton of sense to hit an open Marcus Smart when the coaching staff probably preferred a contested shot from IT.
Adding more playmaking or to-to scoring to the Celtics won't hurt IT's offense, because he is such a devastating shooter off the catch and because teams only stop him by throwing everything they have at him, which would be harder to do if the Celtics had more offensive talent. I guess IT might suck in the Triangle, but in any modern NBA offense he'll thrive.
The reason to be hesitant about committing long-term to him is entirely about defense for me.