Foreign labor is what will keep most of these countries afloat for the following 50 years.
Japan is a good example, they lose about 1 million every year.
And why does the destination country need that persons labour and expertise, but not the origin country?
If the native population is becoming exterminated with or without migration, what exactly is the "country" that needs to be kept "afloat"? Your stock portfolio? Your treasury bills? Your real estate investment?
Ultimately it’s their choice.
Whether a country with high population composed of immigration is still the same country we can look to the Americas. Countries with extreme high degree of immigration and assimilation, yet still very much worthwhile countries. Maybe not the countries the natives from 500 years ago would have imagined, but their culture has survived more than 100 years and contribute significantly to the world still. New Zealand is also a good example of native culture not being wiped out even with assimilation.
Immigration doesn't change the fact of natives dwindling away or not. A nation is the native people, not a name on a map. The exceptions are the United States and other new world ex-colonies. But there was a very dear price paid in blood and tears to make them.
America has had almost no assimilation of immigrants into the cultures which existed there before. Very good arguments have been made that the Enlightenment (or Age of Reason) did originate from native North American ideas and ideals being brought to Europe through cultural exchange, but it's not assimilation on the part of the settlers.
That's almost a uniquely United States problem, not at all as big of an issue in most of the Americas. Only a few countries in the Americas have had their native population pretty much entirely wiped out without any assimilation whatsoever. The US is one of these few countries (Cuba and Hispaniola would be other examples of total replacement).
The rest has had large degree of intermixing or wholesale population preservation. Aspects of native culture is those countries were suppressed historically but are still preserved in some way to this day.
It's also very fair to say sovereign countries today can build a healthier immigration policy than 1500s Europeans with their extermination campaigns. I'd be the last to say that is an example to be followed.
More to the point here: Japan can be exclusively Japanese for another 200 years and die forever, or be Japanese + something for another 10 thousand years. Unlike 500 years ago, they get a choice.
The Native American democracy that the U.S. founders were most likely to know about was the Iroquois Confederacy.
and from other native groups you'll see many statements like:
~ https://collegefund.org/blog/democracy/democracy-is-rooted-i...
IIRC there's a lot of material about the North-North-American fur trade origins piggybacking onto existing Great Lakes and other regions trade networks with the French and the British picking up political and trade habits from those peoples.
( Not a scholar in the field, just a broad reader )
Be aware that the book is a bit academically written and that they want to cover every base in each sentence instead of writing clearly to the point. So sometimes it is extremely interesting and sometimes frustrating and boring.
And the unemployed youth would be working those low skilled jobs today if they wanted to, fact is they don’t pay enough for them and if those jobs are automated away they will still be unemployed.
It obviously suppress wages, which is a necessary condition for capitalism. Any country where it costs 10x to build infrastructure because there is no cheap labor will be less competitive.
Xenophobia doesn't exist in the Netherlands we just hate everyone equally lol.