I'll quibble again. If the same companies were in the S&P 500 then yeah, that would suggest corruption. I think that is not the case.
However, since Glass-Steagall got rolled back, commercial and investment accounts have become mixed. This allows investment bankers to gamble with federally protected deposits. That is corruption, because profits are private but losses are socialized. Pfizer getting guaranteed business from the government with immunity for bad product is the kind of corruption I was pointing out. If there is no risk, then there should be no profit.
IPOs are no longer used to raise capital, but to pay back the venture capitalists and stick the rubes with eventual drop in price after the IPO. That is another corruption of the system.