What’s overwhelmingly changed in my lifetime (since 1980) is that young adult people would rather be alone with no children than take the risk on being unhappy or getting a divorce.
The single biggest change is that the average sentiment now in the “global-west” is “why should I risk my current lifestyle for the risk and pain of a family.”
That wasn’t previously really an option for most people - for a lot of structural reasons. A lot of it was structural repression and the fact that is gone is an unalloyed good.
However it does mean that the expectations for human communities and population growth that have undergirded humanity since the neolithic no longer apply.
We need to fundamentally rethink what humanity is working towards, at a global scale, if the gross population numbers had peaked for humanity.