Here's another way to look at it.
As far as Dak Prescott goes, the Cowboys were the smartest team in the NFL! No luck in him being a Cowboy at all. Every team in the NFL went through a similar process of evaluating players. They all had several chances, including all of round four, to take him. Dallas valued Prescott more than any other team in the NFL, and took him with a supplemental selection. That's not luck!
The Patriots valued Tom Brady more than any other team in the NFL.
The Seahawks valued Russell Wilson more than any other team in the NFL.
The luck, if there is such a thing, is that all three QBs turned out to have much greater value than their 4th, 6th, and 3rd round selections. That's true of every pick at every position. Was Romo, Leary, Staubach, and others just luck? No one knew Roger Staubach was going to have a Hall of Fame career, but the Cowboys valued him in round 5 despite his Navy obligation more than any other team in the NFL.
After round one, every team in the NFL had a chance to draft every player you drafted or signed in free agency. Whether those players turn out to have greater or less value than where you selected them, you deserve 100% of the credit or blame because your scouting caused you to do what no one else did.