There's no problem with him shooting threes, but the problem is his decisions on whether to shoot a three or not. Many of his threes are rushed and require quick releases, which is a skill that is not encouraged for someone who's not a good shooter. Instead, he should look to shoot more open threes, like the ones sully shoot when he's left open outside the arc, giving him ample time to aim his shot. He's way too aggressive in shooting threes, both in nba games and in maine. He should try to take more high percentage and uncontested ones first before trying difficult contested shots in order to improve his jumper.
Another thing I'm worried about is whether his strong finishes around the rim games that he excelled in college can translate to the nba. Even though he has a large body, he doesn't have the handle to get past defenders. And even if he is able to perform layups, he doesn't seem to finish well and at times getting erased by opposing rim protectors. There are multiple occasions that during transition fastbreaks,Smart tried to finish strong with a dunk over his defender, but all these dunking attempts failed miserably. I know I'm a bit hard on Smart (bcuz I have high expectations of him), but I think he's driving game is a bit overrated as he hasn't shown he can consistently do that yet except launching three after three.