Grace builds on nature. God doesn't infuse knowledge into an ignorant man's head just because a bishop ordained him a Priest.
No, you just end up with a very ignorant priest -- one who will make ALL KINDS of mistakes, in the theological, dogmatic, and practical orders, and will scandalize the faithful in various ways. Incidentally, that is exactly what happened in the years leading up to the Protestant Revolt, and which led the Catholic Church to declare in the Council of Trent that henceforth, priests will only be ordained after a formation in a Seminary.
You can't rewind the clock. The Church busted out that remedy for a reason. If you go back to the way things were before Trent, then you go back to times before this remedy.
Apparently we've come full circle, back to the "wild west" days pre-Protestant Revolt. Will history repeat itself, with horribly ignorant, poorly-formed priests doing all kinds of damage to Holy Mother Church, living in concubinage, ignorant of basic theology, literally selling indulgences to the Faithful, etc.?