tf? What 'native countries' do you think exist to people that have been citizens of a different sovereign country since at least 1948? Will they return to Czechoslovakia? Or maybe Yugoslavia?
I'm also sure that the Austro-Hungarian Empire would be chomping at the bit to restore citizenship. Someone tell the Ottomans that the Habsburgs are on the march again.
Source: https://www.dualcitizenshipreport.org/dual-citizenship/israel/
What do you want to do with the remaining few (only 6m or so) that have no grounds to qualify for another citizenship?
I don't want my sarcasm to be overlooked. Your core argument is that someone's ethnicity should be enough for then to 'fall back on' should their country cease to exist. And further, that they would congratulate the party responsible for invalidating their country. That's a stupid and petty argument.