When he's on the ball he can stay in front of guys but he just doesn't have the strength to prevent anybody around his size or bigger from getting wherever they want to go and getting whatever shot they want to take.
Off the ball, he's mostly useless.
He seems to be better off the ball this summer league, imo.
His issue seems to be that he has slow feet. He's not quick enough to get to the hoop on offense, or quick enough to stay with guys on defense.
On offense he can hit open 3's but isn't good at getting himself open. If he wants to succeed he should be constantly moving to get himself open for 3's. Right now he stays on one side and just hopes his defender help off him. This leads to him disappearing for long stretches of games.
He's never going to be an elite defender, or a guy who creates off the dribble imo, so to stick in the NBA he's going to need to shoot 40%+ from 3 and find ways to get himself open for a lot of quality shots.
I would be surprised if he isn't dealt in the off season.