What was unique about Steve Jobs was that he could perform so many different roles within the company. He could convince anyone he needed to join the company, he could ascertain just what kinds of products were likely to be successful, and he could get on stage and sell the living daylights out of the products his company had built. These roles are necessarily going to be performed worse when separated into different executives, just like a basketball player who can play great offense and defense is worth a lot more to a team than ten great offensive players and ten great defensive players.
As Bill Gates said, the (old) Apple model only works if you have a Steve Jobs. The new Apple can't function like the old Apple any more than a car can function without a steering wheel. The best thing Cook can do is transition the company to a more traditional management structure. Will the company be worse off than before? Of course, but it's the best they can do under the circumstances.