Evolutionary fitness is not about "change or go extinct" either (though such methapors were common in the popularisation of natural selection that also led to Social Darwinism). So, while I'd agree with you that most language change is not adaptation to the environment, the shortening of words or the import of words to describe f.e. artifacts of newly acqwuired technologies (from the plowshare to the cell phone) could be considered adaptation.

_{*Lunatic*, n.
One whose delusions are out of fashion.}