I don’t think his ceiling is as high as others for shooting, including undefended FT shooting.
Can he get better? I hope so. Do I expect him to be a good FT shooter in his career? No

His strength is in versatility, but has to be used in spot duty because he has some flaws in his game.

If the team had a HORSE contest, he probably finishes last. That is why opponents leave him open at the 3PT line. They are begging him to shoot the ball.