They definitely did think English was not a language worth engaging with. Even literate people in England barely thought of English as a language worth studying -- they wrote everything in Latin. Certainly the Norman conquerers only bothered to learn the minimum amount of English they had to to talk to the locals. That's why there are so many French words in English.

I think the status of a "creole" language is sort of time limited. After enough people are born speaking it and it's diverged enough from it's origin languages, it's just a language. English probably was very much like a creole language in particular places and times (particularly in northern england after the viking invasions for example).