I’m willing to believe Rav Matisyahu Solomon said that. There were even similar statements from Rav Avigdor Miller zt”l as Joseph can attest.
BUT…neither of them are bigger than the Mishna Brura. And the Mishna Brura called it a lashon chol.
So in psak this debate is over. Nobody can argue on him. Me’kennisht hubben kein machloikes vayl der mishna brura hut gepaskent.
Now, to be honest, Rav Solomon and Rav Evigdor miller zt”l are not arguing. They are holding it’s a lashon chol but still holier than English in some ways, a hashkafic nafka mina not a halachic. I’m maskim kana”l. But lemai nafka mina? I went through the possibilities one by one and eliminated all but one of them, even if you hold it’s holy.
They didn’t mean to use it as an elitist litmus test, that if you can’t speak Yiddish you’re just a worthless Harry and on a lower level. They meant that all things being equal there’s a preference for Yiddish, but not that it’s holier than lashon hakodesh or you are yotzei reading a tefila in Yiddish if you don’t understand. Unless someone paskens you should spend 500+ hours learning Yiddish instead of Torah, this whole subject has no shaychus anymore. It’s not spoken in Litvish circles anymore. In terms of lomdishe geoynus, Rav Asher Arieli’s shiurim are amazing. Linguistically, a rebbe of mine who shtammed fun Europe and listened to his shiurim on tape hated Rav Arieli’s Yiddish, as it uses just a small subset of Yiddish, and not used like a native would use it. It’s creole Yiddish, not the reyne shprach spoken by those who were born in der alter heim. Another rebbe of mine whose father came from Europe told me it hurts his ears hearing the way Yiddish is spoken in Lakewood. He knows how it should be spoken, and the handful of words mixed in with other languages may be yeshivish but it isn’t mame loshn.
קען איך אידיש גאנץ פיין ,אבער עס איז נישט קיין היילעגע שפראך