How do traditionalists discern the difference between novelty and tradition? Easy. If it has not been handed-down from the past, it is a novelty. No pope in history, for instance, has ever conducted anything comparable to Assisi I and II. That this Pope has done so is clearly a novelty. No Pope has ever fabricated a Mass by means of a committee. That Paul VI has done this by intituting the Novus Ordo is clearly a novelty. The idea that I "become the pope" for saying something so obvious is absurd. Nor do traditionalists invent any truths themselves--they follow practices and beliefs which have been handed-down to them by preconciliar popes and councils.
And Peter did not observe the Assumption as a holy day of obligation, nor did he recite the Nicene Creed.
"Easy." "Novelties."