There is a reason they leave him totally unguarded, especially beyond the arc. He simply cannot shoot from out that far and has shown to be horrible when attempting to drive as well.
Plus defensively people were just blowing by him into the paint. Everybody else was having compensate leaving Rocket players wide open for layups and dunks.
For whatever reason, he hasn't been able to duplicate his role in Boston while at Utah. But right now he's a liability and that Jazz bench is thin enough there isn't anybody else to really go to that would do any better.