It's hard for me to square your claim that there's a dominant belief that all humans are blank slates of equal ability with the sheer volume of messaging I see in both government-sponsored and private media about embracing differences, follow your own goals, find your talent, etc.

I see a lot more stuff that would lead a kid to believe "it's ok that I'm not good in math" rather than "I could be good in math if I wanted to be."

Frankly, I think this is actually worse educationally than what you suggest.

We need to find more ways to reward effort instead of pre-existing ability (regardless of how that pre-existing ability is gained... the kid whose parents got him ahead of the curve through high school math and then bombs out after taking university-level Calculus is similarly harmed by the current system as the one who's shunted away from ever being challenged).