It’s true that the long term historic trends of the stock market result in steady growth. That’s taking the very long term view. Anybody retiring in the next 10 years or so should be very cautious about stocks. But young people just starting out should be able to ride out market slumps.
And actually, young people just starting out need to get in the habit of saving in the first place. Get that habit installed, and then decide about how to invest. So many younger people nowadays are not giving a thought to the future and not saving anywhere.
It is a useless habit when you have a berzerko Federal Reserve. What happened to "savings" under Arthur Burns and under Greenspan is just too gruesome to talk about.
The older folks who run the whole place need to get in the habit of living off of current revenue first.