The problem is his shot isn't built for the 3 point line right now. His handle isn't enough to get him to the rim and finishe either. When he does get there he's blowing easy looks.
His best spots on the court are in the center court. He needs to maximize his game there and get his floater and layup going. 3s are just not doing him any favours.
The same issues I had with him on the Kings are present here. I also blame Carlisle. His action is terrible with Siakam on the floor. Should have been fired 2 seasons ago.