I think it's a little extreme to assume "they" wouldn't lift at all though, don't you? I wasn't really saying that exactly, no.
But, to your point, if we consider a genetic condition like kids born with a myostatin deficiency... many of them could go through life never touching a dumbbell and look better then half the guys you'll see at a gym. On the strength side of things, many early strongmen didn't even train. They just ate. My old avi, Louis Cyr, he fascinated me because not only did he not take steroids but he was known to have not even trained... Training wasn't really well understood back then either. He ate like a bull and performed. I truly believe there are guys today with lesser genetics that could use all of our modern training and diet principals and still not achieve some of his feats of strength.
Genetics are what create a Ronnie Coleman and an Andrey Malanichev... I could train and eat and pump gear into myself until the cows come home but I will not achieve anything in the same universe as Ronnie Coleman. Why? Because his genetics trump mine. That doesn't mean I can't achieve great things by working hard though and the same goes for someone with horrible genetics.. but those with the superior genetics are always going to be ahead.