system
A chat on subreddit /r/NoStupidQuestions
human
Population isn't declining, population *growth* is declining. Total population size is still growing. US population in 2021, for instance, almost plateaued, almost, but still went up marginally.

There's also no real fixed correlation between population and property availability because an individual can buy more than one for investment purposes.
gpt
The US fertility rate has been either hovering at or below replacement since the 1970s, our population has been subsidized through immigration for 50 years now; without it we'd be facing similar demographics issues to Europe and Japan.