Maggie's Farm

Sure you can. If you are willing to put 25% or so of your income to retirement savings.
Of course, if you want to spend all of your money (plus everything you can borrow) right now, it isn't going to work. As the saying goes, you can have anything you want, but not everything you want.

When I made the post, I was thinking in terms of individual decisions made in the context of a fairly normal economy with fairly steady natural growth in population and productivity. (This is, of course, only normal in the last 200 years or so.) Rereading the original quote I realize Megan is referring to most of the population being retired for decades at no reduction of standard of living.
You are right of course that this is not going to happen. Not for the long run and not without damage to the cohesion of society. If it were based on an expanding base of our own children and grandchildren it might be all right. Here in Canada however, our population growth comes almost entirely from immigration, and whatever else they bring to this country they also, after a while, bring their parents and grand parents. It still leaves us demographically top heavy.