Joseph,
Someguy has an excellent point. When Jews started moving from Bavel to Europe, and Yiddish started developing to replace Aramaic, it ha paralells to Jews shifting to Mprt America and English. At that time, you could have made the same arguments that you are making now, that Aramaic was the language for learning for centuries, and that Yiddish was a traif language.
By the way, with all due respect to Rav Schach, not all Jews speak Yiddish. Sfardim do not, Jews from Western Europe do not, and the vast majority of North Americans do not.