Unfortunately, this is what happens to any language where there is a dominant language spoken in the schools, on TV, in the media, etc.
My DH knows a number of Yiddish (and Italian) expressions he heard growing up from “the old people” but doesn’t speak either — everything was English for his generation.
But, we DO use a lot of Yiddish words around the house because they’re FUN — kvetch, tchatchke, shtick — and most of the Italian swear words.
And, long may those those words live — and let’s keep them alive!!