Avi, of what consequence is it that there are communities that do not speak yiddish? Are you implying that sefardim are for some reason, an authority on authenticity?
Yiddish is a rich spoken language with Torah sewn into its fabric. Modern hebrew is the polar opposite; it is lashon kodesh with kefira and foreign garbage sewn into its essence. Its originators were bent on destroying Torah forever and replacing it, rachmana litzlan, with a secular jewish identity.
Speaking a “creole”, as you call it, is based on rishonim and achronim who write that lashon kodesh is too holy to be used as a spoken language. There is a reason why Jews in Bavel spoke a Judaicized Aramaic, sefardim made ladino, Jews living in arab countries spoke a Jewish Arabic, ashkenazim made yiddish, down to our own time, when a newcomer would recognize hardly an intelligible sentence spoken by a yeshiva bochur.
Modern Hebrew was an evil that was left alone, under the chazon ish who famously said that it is a battle that we already have lost.
There is a reason baalei teshuva are drawn to the warmth and passion of yiddish speaking jewry. A shiur is just not the same in English, or hebrew for that matter, but hebrew shiurim are generally more of a “yeshivish” Hebrew. An argument can be made to corrupt ivrit and make a yiddish out of it; as I’ve seen in certain places, that is already the norm.