I've noticed the same in Finland
"blah blah blah and then I died blah blah blah good game!"
But I do agree that some languages are more inured to this than others, such as British English. Having enough native speakers generating new OC in the language also helps prevent a fashionable trickle of loanwords become a flood that threatens to sweep everything away.
It's the same in Sweden, English has become so commonplace you see it everywhere. Probably half od all public adverts on bus shelters and the like are written in English for no apparent reason other than it's fashionable. "Yes" has become a fairly common alternative to "ja". But overall, I don't worry too much than Swedish is really under threat or that in a generation English will have taken any deeper root.
French is definitely the language of choice for pretentious twits who like to do this.
It's always been a thing in our family, in my childhood it was Kswahili and French, the former because of my parents history and the later because of family holidays en France. After German/Russian/Latvian exchange students stayed with us there would be other phrases.
Nowadays I drop the odd "privyet" (RU), or "ca va?" (FR), or "<signing>" (BSL) but it's mostly domestically, sometimes that leaks in to the public arena ... does it offend?
Perhaps people aren't showing off but just doing something they think is fun.