I think the fundamental component is house prices. Our ancestors had much cheaper housing as a multiple of the median wage, and could mostly afford to buy based on the paid labor of the father alone.

Those same ancestors are still sticking around, living in those houses, and demanding tribute in the form of medicare and welfare payments (2/3rds of the federal budget).

I'm only saying this to spark and extend discussion: but a society in which Euthanasia is mandatory at age 80, with housing and monetary resources freed up for younger generations, is likely to be a happier and better place to live.

Alternatively we greatly limit immigration (including cross-border) - to only the most skilled and intelligent immigrants - and we create some kind of huge carrot/stick to get older people out of big houses and into smaller, managed apartments. A comprehensive land value tax, with discounts for families with children under 16, could solve this.