Joseph, Rambam, Ramban, Rashaba and Ritzva did not speak creole German. Neth di the Radbaz, the Arizal. the Chida, Rav Chaim Palaggi, the Ben Ish Hai, etc. Rav Ovadia even made fun of the Ashkenazi pronunciation of Hebrew.
It, When Rav Charlop first met Rav Kook he addressed him in creole German. Rav Kook said “Being that you are new here I will not hold it against you. However, you should know that one does not address me in Jargon”.
I reiterate, “Yid” is a pejorative in English. Archie Bunker, in fact, used it.