IIRC it was the more decentralized system in the Roman legions that made them effective. Everything in Rome was made more or less so they couldn't rely on a single gifted man all the time, except for the Dictatorship.

The system worked fine: on one hand even if they couldn't match the tactical genius of troops under men such as Hannibal it did not take extraordinary competence to fight with them as much as with a Carthaginian mercenary band.