I agree with your observations. The future will not be as bright as the past, the population boom was already squeezed for the gains. Immigration at the levels needed to change this are unpalatable to most electorates, and with total fertility rate dropping across the world, it's important to be mindful that net migration to Earth is 0 (slide 39). As the economic future deteriorates due to the ever increasing drag of these obligations, I'd expect total fertility rate to continue to decline at present rates (if not slightly accelerate). This creates a self reinforcing feedback loop. A "Demographic Doom Loop" [1].

Happiness is reality minus expectations.

[1] https://x.com/KenRoth/status/1753526235173450213 | https://archive.today/rY4WG