First, remember it was "sky" hook when Kareem did it because he had mastered the skill of putting the ball at the very top of his extended right arm before shooting it. At the same time, he got some air. So at his height and with his jump, the shot looked like it was being dropped out of the sky. For everyone else who shot it, they never had release points like Kareem's.
Key to Kareem's mastery of the shot is that he started shooting it in the 4th grade as a way of getting shots off against older and taller players. Then at UCLA, the NCAA did not permit the dunk, that forced Kareem to keep practicing the hook, to refine it and to extend his range. Another part of Kareem's mastery was knowing how to respond to the pushing and shoving that is routine in NBA post play. So it was routine for him to adjust to the defender's hand on his hip or waist. Or to the bodying up to him. Or the double teaming. Finally, consider the range he had extended himself to by the time Magic came on the scene: he was routinely hitting the sky hooks from as far as 18 feet out. Dig up that video of Magic's very first game as a rookie where Kareem hits the last second 18 foot hook shot that wins the game... Made it look easy.
So Barn thinks it's an easy shot, eh? It may be easy to get started, but mastery like Kareem's is something else. Think of the other guys who shot hooks, no one ever had Kareem's range. No. One. Further, when I played against guys who used hooks, I'd shove them in subtle ways designed to throw them off. But Kareem mastered responding to defensive tactics like that.
It's a beautiful looking shot yet I despair of ever seeing anyone master that shot and rely on it to become a dominant scorer in my lifetime ...
I shall be telling this with a sigh
Somewhere ages and ages hence:
Two roads diverged in a wood, and I--
I took the one less traveled by,
And that has made all the difference.