What if the test is not great at evaluating the capabilities of a person to do their future job. Maybe preventing a person that does not understand differentia

What if the test is not great at evaluating the capabilities of a person to do their future job. Maybe preventing a person that does not understand differential equations from being a doctor, English teacher, event manager ... „I literally do not give one flying fuck.“ The person who cheats, will give no f** about your opinion either.