No CEO of Apple, except Steve, has ever demonstrated having what it takes to make Apple grow and progress. A three year old child could have done as well as Cook. Apple is like a bulk ore carrier that has so much momentum that if you turned the engines off, it would sail on for 40 kilometers before it coasted to a stop.
Except in Apples case, the "bulk ore carrier" appears to be actually getting faster. We have increased money pouring in the bank (even with increased R&D investments increasing), no real evidence of product release slow down (in the iPads case increased to six monthly), installer base increasing exponentially (think iTunes, apple software, third party software)...... and all this in a massive market turn down (the bulk ore carrier is actually going up hill in your analogy).