For instance lets say there's a patron saint of infants, but that a recently canonized saint is clearly superior to the previous one when it comes to infants.

Is it not then warrented to make the previous saint step down to leave the place of patron saint to someone who is holier?

Catholics, Orthodox, some Anglicans and some Lutherans believe in patron saints. But considering that Catholicism has the most well defined grasp this doctrine I would prefer an answer which agrees with Catholic theology.