> the S&P 500 no longer reflects the actual market

Well it was never intended to reflect the full "actual market".

> no longer an adequate benchmark

According to your definition it never was. However there were and are plenty of other index benchmarks which serve different purpose. Its just that S&P 500 managed to become the most popular one, why did it happen if it was always inherently flawed?

Like they didn't even add Microslop for 8 years...