Even still, Josh did enough with subpar talent around him both in college and the NFL his first few seasons to show that there was something special about him.
I have no doubt that Mahomes would have shown that he was ready for the NFL and had what it takes but that's basing it on the fact that he would have had a year to sit and learn behind Turod.
As for Darnold, USC QBs have always been a flash in the pan to me. They are great in college and are bad pros.