Case in point: I moved to Finland as an immigrant 9 years ago, with nothing but a backpack, girlfriend and $12k in my bank account. Within 7 years, we paid down the mortgage for 100 m2 house in the capital area, while raising two children, with one above average and one below average income. And I don't feel like we were materially deprived in any way.

I think the main culprit is couples settling down way too late in their lives. Instead of settling down at the age of ~25 and combining two incomes to pay off the mortgage principle, we have two adults, each paying ~$700/month rents. When they finally move together at the age of ~30, that's almost $100k that went down the drain. The baby-boomer generation used to move together at even earlier ages, 19-22.