Avi K is right. Our common language is Hebrew. Why arent’t these rabbis speaking Hebrew? That is the most basic thing a rabbi should know. Forget Sephardim, he VAST majority of American Jews do NOT understand Yiddish.
Yiddish is a part of our collective fabric as a people it is true. But not unifying, not common. Just like Gerush Sfarad is part of our collective history even though not all Jews experienced it.