He appears uncoordinated. Poor balance, high center of gravity, slow reflexes and a poor handle even with his strong hand.
It's just difficult to mold a common 6'6" wing with those flaws into a good NBA player. I'm not sure how fixable they are in the first place, but there's too much competition at his position - he doesn't have time. Even since we drafted him, we picked up an arguably better prospect at SG/SF in Hunter and an unquestionably better prospect at SF in Brown.