college. School and personality aside, consider this:

His shooting % didn't improve in college. He's a career 38% 3pt shooter on a college team that ran a system that was about as good as anyone in country at getting guys open 3 point looks - he basically was asked to be Kyle Korver but hit at a lot lower rate. He had big guys like Winslow, Tatum, Bagley, Okafor, Carter and Ingram who would routinely draw double teams inside and hit Allen wide open; he had other shooters like Luke Kennard who opposing teams were more concerned about helping off of and leaving open than they were with Allen.

He doesn't play defense. At all. He doesn't move laterally well, guys routinely took him off the dribble. He was slow to rotate on the perimeter to help. He wasn't strong fighting through screens on defense.

His passing is average. He can find open players but doesn't anticipate the open pass before it presents. That worked against Pitt, Wake and GT, but not against quick defenders which is most of the entire NBA.

He's basically a smaller, less potent, less aggressive, less defensively capable Joe Ingles.

He may be a gym rat and he may be willing to work hard...hopefully for him and the Jazz that is the case. But he's an average player with a low ceiling.