It sounds like you are disputing the premise but at least at a glance it seems obviously true. Why do you think surviving previously unsurvivable ailments or living a normal life with what would have otherwise been a debilitating illness past reproductive age isn't partially nullifying natural selection? And is the billionaire with 11 kids the normal case or just maybe slightly cherry picked?
Because circumstances have changed, selective pressures have changed, and an ability to grab the half gnawed finger bone from your fellow ape-creature is less valuable now than it once was. In a world where the disabled can write code or whatever, they have evolutionary value. I don't disagree with the premise btw of devolution a la Idiocracy, just think your specific argument falls flat.
