This is a valid point, and folks who take a long-term view tend to come out ahead over the long periods, even going through worse disruptions than COVID (which, in my view is not that big when compared to wars, revolutions and such).

I am not a financial planner, but just a few thoughts. First, folks who try to invest in crashes or divest on peaks tend to do it too early. Most of such events give you more than one opportunity to buy/sell and not being first in/out can give big advantages.

Second, we did not (yet?) see a big drop. A rise of 20% would put S&P at or near all-time highs. For comparison, during the 2008 crash, S&P dropped by over 50%, so the rise back would give you ~120% return. Thus the reward for "catching the knife" today is much, much smaller than in 2008.

Finally, a lot of stocks are now indexed and held in retirement accounts. Many folks there hold more than they should in stocks because they have been going up and seem to be the only game in town beating inflation. And all advisors say "leave your retirement accounts as is, long term view, yada yada". If a significant number of people start moving retirement money out of index funds, which they might do in uncertainty, there may be a lot of pain for stocks. For example, many smaller stocks just do not have the trading volumes to withstand even a moderate sales increase driven by index funds. My 2c.