He can shoot. But he needs to be in rhythm and have the ball in his hands. He's not a great spot up shooter. And doesn't move well off the ball like most 2 guards.
The problem is he's not getting touches and hes playing scared. He. Won't shoot so they aren't passing to him. On his Iso he can get to the basket but cant finish cause hes either too weak, not explosive or too short.
That was possible in highschool and college but not against NBA defense.
Rivers is the type of player to dominate the ball or just disappear.
Basically he needs to change his game and become a 3 point shooting/point guard like Curry.