There are multiple simultaneous problems:

- A political unwillingness to reign in private capital that's exacerbating resident housing shortages / rent increases (read: AirBnb)

- An infrastructure underinvestment in building sufficient new housing (or motivating current housing owners to densify)

- An underappreciation (Germany) that one can't switch energy mix at nation-scale without first building replacement capacity

- (Europe at least has far more child-rearing-friendly policies than the US)

But all of that is a "maintain demographic shape AND ___" problem.

Countries with inverted demographic pyramids go financially south very quickly.

At best, there are some extremely hard compromises to make (higher taxes on a smaller working base, or decreased social/retirement benefits).

At worst, there are no solutions to balancing a budget and things spiral out of control quickly.

It's underappreciated that "young immigrant labor is funding the country".