As much as I disagree with his thesis here, the entire point of it is that YC wants to and does fund toy companies. So they're trying to solve the exact problem you're railing against.
People like Mark always had the security of their family's relative wealth and security on top of their general status in society. That's not a luxury afforded to most, and certainly not those from low-income backgrounds.
And yet, at least some people do now have that luxury. It certainly isn't impossible for lots and lots of people to afford some degree of something pretty similar tho.