Some people are. And I will one day, so not sure why you think it doesn't matter. Will it return? Sure. But that still leaves 1-2 years with no growth.
If you’re not ready to retire, you have much time for the value of your portfolio to recover and continue to grow.
“Time in the market” is the primary consideration, but also proper diversification (less growth, but also less risk) as you get closer to retirement.