We already have that word

“I still think we need a word for cultural self-genocide.”
– Stephen Green, Instapundit

We have it. That word is “immigration”.

“Having spent some time perusing the genetic imprints of invaded populations, it is clear that if the warriors coming from the Eastern steppes left a cultural imprint, they certainly left their genes at home. Gene transfer between areas happens by group migrations, inclement climate, and unaccommodating soil rather than war.”
– NN Taleb, Skin in the Game

Immigration is not “good for the economy”. Immigration is the precise opposite of “who we are”. And as genetic science has conclusively proven, it is quite literally worse than war.