Giddey never progressed his game. He was able to showcase a lot more as a rookie when it was basically just him and Shai dominating the ball. As they added other players that could do more things, they didn't need a ball handler like him on the court who can't shoot and just makes some fun looking passes. Big difference between him and Amen. Amen can do so many other things to where even with a worse shot he's still valuable to have out on the court.