Every country on earth is trending downwards. A lot of currently immigrant-exporting countries (e.g. Vietnam, India, Mexico) have sub-replacement levels of birth. They're going to have absolutely massive problems in a few decades when a lot of their youth have left and they're stuck with an inverted population pyramid.
There's a tendency for people in developed (particularly western) countries to feel entitled to immigrants. It's weird to think you'll not only have people changing your diapers when you're 90, but that your country should actively bring in people and deprive poorer countries of similar care, then leave those poor working class immigrants to fend for themselves once they're old.
It's the same mindset that drove society since the 1950s: it makes my life convenient, who cares if it makes life harder for people far from me or after I'm dead? And now we're all living with the accumulated consequences of all that (depleted ozone, climate change, ocean acidification, microplastics, oceans stripped of life, teflon pollution, deforestation, CO2 rising rapidly).
The world needs better solutions.