People don't like to hear it, but getting replacement population in is pretty much required to avoid eventual chaos.
Take a look at most of Europe or even a lot of the USA.
Realistically just to have a stable population and stay where you are, most people need to get married and try to have at least 3 children per couple (no you can't have fractions of a kid).
Generally the "educated, native, wealthy, productive, prosperous" People are way too selfish by and large to want to raise a kid, let alone at least 3 and even for that matter get married.
All is fine being selfish pricks for a generation and such, until that whole generation starts getting old / retiring, now oops... who was going to pay for all our retirement (because you let your government spend all your "retirement taxes" instantly, long ago), who is going to be wiping your asses and bringing you meals in your nursing homes?
What young people having grown up in selfish time have any interest in paying crushing taxes and working away to take care of / support an older selfish generation?
= Chaos in society.
Bring in breeding replacements, and make up the taxes on gross economic activity even if actual direct income taxes are down a bit.
Of course you give them tons of welfare but once things get rough, you start cutting that back a lot.
Not a great plan, but considering western types are unbreeding themselves into collapse, well...
If you don't breed, the ground will be taken up by those who will...