They aren't wealthy by any means, like the retirees out here in California who have a million dollars (or several). But between their stocks, the home equity, the two social security checks and a small pension my dad got from spending time at a job at the city government they'll be alright.
It's also easy to shield yourself from massive losses through diversification. Vanguard even had someone talk them through selecting funds, even when they didn't have much money to invest. I also got them to pay off loans (cars, credit cards), which is the safest investment you can make for the returns.
I should also emphasize that, having started so late, stocks could never be their primary source of income. At a reasonable withdrawal rate I think they'll get about about $15-25k per year. Most of their income will still be from social security. But on a long enough time scale one of them will get senile or cancer or something, and we'll thank god for that big pile of money when it's time to hire help.
Personally, if I see the stock market dip like that again I'm going to double down on my 401(k) contributions.
I wouldn't let expected market returns impact the amount you feel is appropriate to save/invest today.