Is one to submit to the authority of all the Popes or merely the current shepard on the throne of Peter?
Quo Primum states: "We likewise declare and ordain that no one whosoever is to be forced or coerced to alter this Missal, but that this present document cannot be revoked or modified, but remains always valid and retains its full force--notwithstanding the previous constitutions or edicts of provincial or synodal councils, and notwithstanding the practice and custom of the aforesaid churches, established by long and immemorial prescription--except, however, if of more than two hundred years' standing."
Because this is such a tired old SSPX error, and because I cannot say it better, the following is from Catholic Answers This Rock magazine:
There are several things to note here. First, Quo Primum was a disciplinary document, not an infallible doctrinal definition on the Mass. As such, there's no reason to think it's irreversible. [emphasis added]Second, Pius V's purpose in Quo Primum was to establish standards for the celebration of Mass throughout the Roman rite, not to determine how Mass would be said until the end of time. While allowing for a few exceptions, the revised Missal of Pius V was to be the norm.
Pius V wanted to ensure that "conservative" priests of his day wouldn't continue to celebrate their own local liturgies at the expense of the newly revised Roman Missal. In other words, he suppressed many local liturgies to establish uniformity of rite according to the needs of his day.
Third, the statement in Quo Primum that "no one whosoever is to be forced or coerced to alter this Missal" wasn't aimed at future priests who might dislike the liturgical changes of a future pope and who wanted to retain Pius V's liturgy. It was a safeguard for priests of that day who followed the revised Missal rather than the liturgy of a hesitant local bishop.
Fourth, when Quo Primum did mention those who were forbidden to alter the revised Missal, it said nothing about future popes. After all, how could Pius V have forbidden his successors to revise his Missal? If Pius V had the power to change the liturgies of his predecessors, why shouldn't future popes have the power to revise his? After all, his authority couldn't be superior to theirs.
Fifth, there's no evidence subsequent popes were aware of any intent by Pius V to limit their pastoral authority over the Church. Since the sixteenth century there have been numerous changes in the Missal of Pius V approved by various popes. Although none were as extensive as those of Paul VI, there were changes, a fact which refutes the Lefebvrist reading of Quo Primum.
Matters of discipline are not infallibly promulgated. If you argue publicly in contradiction to papal teaching and separate yourself from the bishop of Rome, however, you separate yourself from the Catholic Church.