Very few people have the inclination or desire to accomplish intellectual greatness, though, and that's enough to keep most people out regardless of ability. When you only look at people who have that inclination and desire, many people openly admit to lacking ability compared to others.
The idea that all humans have the same potential to do anything is, frankly, something people tell their children as an encouragement to work hard, but is not really true, or honestly believed by adults. Not everyone is talented enough to be a professional athlete or a tenured physicist. Everyone who's tried to teach has noticed that some people pick things up better than others. I'm not talking about the people who aren't interested or don't care or don't work hard enough--even among the motivated students, some do better than others. And no matter how hard you work to pick up the people who are behind, they can't quite catch up. And if you invest just as much effort in the better students they only get further ahead.
Consider the evidence. How likely is it, really, that there exists some undiscovered, magical way of evening the divide?