This means during prolonged periods of peacetime, a form of regulatory capture happens where the metrics used to evaluate promotion become decoupled from actual fitness of purpose.
For example, since success in academics is usually the first requirement to even start in any position above the most menial, anyone who finds it difficult to toe the line and waste hours listening to someone drone on about a topic totally unrelated to their purpose in life, or enthusiastically embrace make-work homework assignments, will likely have a hard road, no matter how well qualified they might otherwise be.
One could argue that the U.S. military in particular has had a tremendous opportunity this last decade or so to conduct exactly the kind of wartime evaluation you're talking about. But I wonder if the evaluation metrics are optimized towards peace-time?
In many respects, David Petraeus is the perfect embodiment of these political principles. He published, he politicked, he maximized his media exposure, and he hobnobbed within the right DC circles. I'm not qualified to judge whether or not he was as good a leader as many believe him to have been. But he was certainly a top-notch political operative.
(Other government agencies, e.g., the CIA, have very similar internal political incentives. The game is almost the same. This may explain, in part, the fluidity between military leadership and Agency leadership).