Cousins play is all over the map, he can't be everything. He can't be asked to be a defensive anchor, and rim protector/inside scorer, and be a stretch 4/5 ball handling/facilitator. And anything else the Kings can think of.
The Kings are a really dysfunctional team, 3 centers, nobody defends, no team ball movement, and most of all no plan. Everyone is on improvise mode. Maybe just too many strong personalities on one team.
I think if Cousins was asked to play a type of ball movement offense/team ball, in a stable environment, with a defensive game plan, with everyone on the same page, he wouldn't be so erratic, personally and in his play.