His offball defense is lacking and his jumpshot isn't there. For a team with championship aspirations he isn't it.
Doesn't pass the ball like Dray, and doesn't have the same defensive IQ. His PT was gonna suffer regardless imo.
That's why he needs to leave. Warriors are in win now mode as they should be. Their unwillingness to sacrifice any of that for Kuminga's development is gonna hurt him. It's just the wrong team for him.