Ahhhh. I misunderstood. However, there is more to the Faith than simply the Nicene Creed. But it's not worth splitting hairs over. The Catholic faith has evolved over a long period of time, be it with respect to investiture, indulgences, ritual, etc. A medieval Catholic wouldn't be able to preside over a modern Mass, and would probably be shocked by the teachings out of Rome today (not that that is a bad thing).
Heck, a Protestant could claim to be following the "creed" established in the New Testament (as many more fundamentalist sects do), which has the longest pedigree of any Church document. Surely you wouldn't argue that the Church hasn't changed since 383, would you?