He just hasn't developed elite basketball intuition. He's the kind of player that can get hot and still produce boneheaded plays. And when he's not playing well then you can just forget about it.
In reality he should be a mini-LeBron, but he just doesn't have that feel for the game at all. And that last point is typified by his crappy shooting. Effectively scoring the basketball is one of the most finesse skills in all of sports, to the point that technique almost takes a backseat to rhythm and tempo. And athleticism is almost not even necessary.