This is the standard Lib-tard argument whenever the market drops or a segment drops. Yet the plan the is being discussed is over a 45 year history, and a balanced portfolio market has always outpaced the government return on Social Security, and by a huge margin. Real estate is simply another segment of the market, and an important part of a balanced portfolio.
It all depends on when one retires. Let me give you an example.
My wife worked for a town that had a pension plan. (Government job.)

When she quit, being an accountant, she took all the funds and invested them in term deposits This was around 2004-5. Had she left the funds with the town the total value of her retirement account would have been considerably less than what it is now.
People who retire now or retired a couple of years ago got the shaft. A friend of mine lost approximately 30% off the value of his retirement account and he's close to retirement. He has a problem.
Let's use some figures as an example. If someone had $100,000 and lost 30% they'd have $70,000. Not only have they lost the interest on the missing $30,000 but, in all likelihood, they would have to draw on the principal. Let's say they take $2,000. Now they have $68,000 left. Then we have year two and year three and by year four the retirement account is close to $60,000. They will never recover.
The person who didn't retire still has the $70,000 and when things improve they'll see the profit from $70,000 as opposed to the profit the retiree will see from $60,000.
One does not have a large window in which they can retire. Usually it's a matter of a few years and many, seeing a bad year, hang on hoping for a boost and we all know what happened this time.