ZDad: It’s sad that you couldn’t communicate with your great-grandfather, but you could just as well blame your mother for abandoning yiddish instead of blaming your great-grandfather for not learning English. The reason more Jews speak English today is precisely because such a lack of continuity, which is manifested in many other factors of assimilation.
I’m not trying to be too personal here, I just want you to gain some perspective, so please don’t take it as such. I’m talking about America and using your words to illustrate my point, even though I hardly know anything about you. I don’t I want you to point fingers at anybody either, especially not your mother, just realize that there’s another side to every coin.