So clearly, for the individual, the optimal strategy is to simply invest in index funds and just wait. But a new question that is being raised is: "what happens if everyone only invests in index funds?"
This has been answered a thousand times. Everyone will never invest in index funds. What will happen is more and more people will invest in index funds until there are so little people actively investing in the stock market that the ones that do are able to beat it. However, them beating it will only net (after their fees) the same returns as index funds thus striking a balance where index funds match the performance…
You have way too much faith in people making well informed decisions.