That it tends to become a caste system with extra steps (which steps provide a defense of the system as “fair”) is one of the chief criticisms of meritocracy (and criticism of the idea is where we got the term itself)
i very much beg to differ. A poor but high aptitude student today is able to escape the "caste" they're born into. Under a true nepotistic system, this cannot happen no matter how much aptitude he/she possesses.