That is still quite young and I am sure he can improve, Lebron added shooting to his game like after 30 years old, so I am sure Giannis can improve, however how he plays is obvious to everyone now and its rarely ever possible to stop him, so what makes people think he will somehow change the awesome unstoppable way he has and somehow become something else?
It seems you have forgotten how the Raptors stopped Giannis in the 2019 conference finals. All they needed to do is block the driving lane of Giannis, denying him the paint and he is totally shut off.
I doubt that is even logical let alone possible. Definitely, he can suddenly start practicing shooting fadeaways more and with the reach and arms and height he has became an improved version of Nowitzki but does he need it? Dude already can do whatever he wants, its really mental to thing he needs to improve from his current self.
There is nothing wrong with improving and becoming a better version of yourself as a player. Adding shooting, whether fadeaways or not, is a good arsenal for a basketball player. What mental is thinking that he is too good to need to improve his game? Becoming stagnant is how you become obsolete in the game. It is better for him to learn it now, do it now. It does not matter if he needs it now or not. What matters is that he keeps on improving himself until he reaches his maximum potential. And use that full potential to bring in the chip to Milwaukee.