IMO to have big traps you have to start with genetics for them. Don't get me wrong, obviously doing shrugs, deadlifts, ext will stimulate them, but at the end up the day most muscle groups and how big they can get is all genetics. My traps and chest I can just stare at them and they will grow. Arms on the other hand....not so much. lol
Yeah I agree that genetics play a big role, I have always had good traps even when I didn't work them out. I'll try the suggestions given to me here, maybe shock them into some more growth.
Maybe you could stare at mine for awhile haha, I could use some of those stare gains.
No supplement beats hard work