Garappolo has proven nothing
Wilson is good but not great and relies on his legs too much.
Prescott is showing that he needs Elliott in order to be effective but the jury is still out on him.
Cousins is mediocre at best.
Now to answer your question, the answer is yes to both. Teams get lucky. Brady, Warner, Romo, are hall of famers or who have put up hall of fame numbers who were either drafted late or not drafted at all. Then you have high draft picks who looked like world beaters in college who were drafted high but who were bums in the NFL(Vince Young, David Klingler, Akili Smith, Andre Ware, Ryan Leaf, JaMarcus Russell). As for us, yes Leenart was a bust but he started out with promise. Whiz literally killed this kid's career.