Those mercenary slaves were actually a big part of why the Ottomans did so well to start with. When they boys were taken they were given exams and the 10% that did the best became bureaucrats in a sort of version of the Chinese system. Exam based bureaucracy is a Big Deal when you're competing with aristocracies.
But eventually offices became hereditary and the normal sort of Chinese late dynastic rot set in.
But eventually offices became hereditary and the normal sort of Chinese late dynastic rot set in.