If something is taught dogmatically, it was true before it was taught. It didn't begin to be true when it was taught. If your reading of the canon is correct, then would it not have always been true that no one could change the rites without offense? And yet we know that saints did this very thing. Was St Gregory the Great acting contrary to the faith when he added to the canon?
Dear jdfaber,
The dogma of the Immaculate Conception has not been proclaimed when St. Thomas was alive, he was free to express his opinion on the subject. It so happens, he was wrong.
Is it true that upon Pope St. Gregory's proclamation, the Roman populus was ready to kill him? Or is it just a wishful story of an abused Catholic? If the story is true, it is a witness to the Faith of the people of that time. Where was the same fervor when Pope John XXIII introduced the name of St. Joseph? Where were we when Pope Paul VI got rid of the Canon altogether? What is the state of our Faith?
The words "Diesque nostras in tua pace disponas" remain in the Canon as the part of an organic development, since the dogma has not been proclaimed till Trent.
Which other saints added anything else to the Canon?