In my view, it's not (directly) because of the post-war optimism. That period saw great advances in almost every area of life. It's the period of stagnation that followed that's causing the hangovers. In the political and social arena, we stopped innovating in the 80's. We were just coasting on the stuff we built before, without clear direction and without new goals. Everything we had was "good enough".
Except that we didn't work to maintain what we had. Education systems were gutted, public infrastructure was sold off to the highest bidder (Bayh-Dole act, every privatization of government services that followed), maintenance was deferrred (many roads and bridges are deteriorating in both Europe and the USA, 80% of nuclear plants in operation today will reach EOL in roughly ten years without replacement).
Yes, periods of prolonged prosperity aren't unique, and they always end in one of two ways: destruction or decadence. Take your pick.
for almost a hundred years we've seen each generation get wealthier
This isn't true. The last generation to be wealthier than their parents were the baby boomers: https://www.visualcapitalist.com/charting-the-growing-genera... . The average wealth per person has been decimated since then: Generation X is only half as wealthy as baby boomers, while the average millennial is ten times less wealthy than a boomer. And this isn't just because of their current age:
> In 1989, Baby Boomers and Generation X under 40 accounted for 13% of household wealth, compared to just 5.9% for Millennials and Generation Z under 40 in 2020.
So in 30 years time, the younger generation lost over half its wealth to the older generation.