Going by your "logic", you must not believe in the Holy Trinity because the bible doesn't specifically state the Name, nor do you believe in the Immaculate Conception, the Assumption, or the Coronation, because they aren't specifically stated in the bible. Forget holy tradition, we have to take a literalist word-for-word view of written precepts whether it's canon or papal decrees.
Be fair, Tourmalet. You are pushing your argument too far, specifically in that the Bible and Tradition are simply irrelevant in the present context. That is, the matters you cite are all dogmas, not matters of papal jurisdiction—or rather, each one lost any jurisdictional dimension it might ever have had once it was dogmatically defined.
I simply do not know enough of the precise circuмstances surrounding the drafting of
Quo Primum to weigh in one way or the other on forlorn's assertion regarding the bull's primary target audience. His assertion does, however, have the great merit of being prima facie defensible, which is more than can be said for assertions regarding the bull's permanently irreformable character. That is to say, it is by no means plain from the language of the bull that it indissolubly links the celebration of the Roman rite with the content of the Faith as defined for all time.
Surely the plain meaning of the power of the Keys is that it confers upon each and every pope enormous latitude to act as he chooses, for good or for ill, while being answerable to God alone—save in the few exceptional circuмstances whose character is so resistant to definition that Bellarmine and other authorities cannot even agree upon what those circuмstances are or what options are available to those who would counter the abuse!