You’re not wrong in the one dimension that people preserving a culture are by definition “losers” (otherwise it would take no effort to preserve), why don’t we try not punishing kids for speaking their mother tongue and see how that goes for a while?
I guess if that's what people believe, it may be tough to convince them otherwise... but IMO, it's really valuable to think about how the "winners" of history navigated tough moral challenges, and often did things that we can now identify as harmful.
In this case, it's not about making historical missionaries feel bad about themselves for "winning" -- this article (in my read, etc) is concretely about trying to avoid repeating these mistakes in modern tech, specifically NLP and translation. We can (hopefully) do better as a society than "might makes right"!
Or maybe its a sign that winners couldn't completely eradicate it because it occupies a niche in a more optimal way than the winner. Infact, we have seen winning cultures fail while the niched "loser" culture maintains, only to thrive after the downfall of the temporary winner.