Considering around 1/3 of students at schools like Harvard are Legacy Admits who would never otherwise get admitted on their merits, I don't think your argument holds much weight. You seem to be admitting that they are selecting for elite education, if they were selecting ambition and intelligence there are countless people like that who went to a big State school instead of Stanford yet they are not represented in "Elite" firms whether that's VC, IB, Tech etc..