The things you mentioned have been tried in several wealthy countries and they don’t work. Even if they did, they require a lot of societal wealth to implement and once the global population starts declining so will the economic output and consequently tax revenues, that’s a 1-2 punch for living standards which will also fall. Our economy is 100% dependent on healthy young people which means no kids, no economy. If fertility rates get stuck at 1 or below 1 then the population will halve with each generation and the only thing that will stop it “naturally” is the complete collapse of global civilization and a return to tiny feudal states ruled by probably religious fundamentalist warlords where 99.9% of people are subsistence farmers. Even if you like that outcome for some demented reason consider that there will still be the rusting leftovers of our technology for the idiot barbarians to play with.