For most people the absolute best advice, the only sane advice is get the fuck out now! If you are willing to take risk, bear markets can be very profitable. Lots of people did exactly what you say and adjusted for inflation lost a decade because of it. Returns on the S&P have been anemic since the top of the market in 99.
The average annual return on the S&P500 over the last 10 years is 4%. The average annual return on the S&P500 over the last 5 years is 11%. So the average annual return over the last 10 years hasn’t been great, but it’s certainly no disaster. The 5-year average annual return is very good.
Even if someone put all their money in at the top in 2000 (when the S&P500 topped out at approximately 1500), they would only be down 12%. Adjusted for inflation they would be down more than that, but that’s still not bad for putting all your money in at the all-time high (something that dollar-cost averaging would prevent).
Please post the next time you go short. Since you think it’s “beyond stupid” to dollar-cost average from these levels (down approximately 12% from an all-time high), I want to see in real-time how a real trading genius does.