Westbrook is 33 years old already and near to past his prime. He is athletic I agree with that and yes he is one of the most athletic and most explosive guards in the NBA. The problem is that, he doesn't fit with the system.
I agree with this one. Westbrook does not have the same explosiveness that he have before. He is still very athletic compare to others but the explosiveness that he needs to drive into the basket is simply lacking now. He cannot run as fast or jump as high as before.
A common issue to some basketball players that relied only on their speed and strength. That is why more and more players really want to practice their shooting, big man or not, it helps to prolong their careers. Imagine Giannis 10 years from now if he cannot develop his shooting. Although the guy is developing and is somehow smart. Maybe he can play basic simple basketball like Tim Duncan when his body is past its prime. I think Westbrook's ego is also a problem. That would be hard to teach. Even during his younger years with KD and Harden, I think most of the time he's got more attempts than KD and others.