That's because the Church never issued an apostolic constitution preventing changes to the missal before Quo Primum, and the Tridentine Mass remained 100% Catholic which means there was no substantial change or novelty to the Mass. The "mass" of Paul VI is a novelty and not Catholic, and it, thereby, violates Quo Primum and is unlawful. Even if QP was never decreed, the new "mass" would still be illicit and not Catholic. So you can play mental gymnastics with Quo Primum and rationalize that it doesn't prohibit substantial changes to the Mass, but that doesn't excuse the new order "mass" as being licit and Catholic.
That's what you're doing.
Wrong. See my previous comment again which you obviously can't comprehend or you stiff-neckedly reject due to pride.
As per Quo Primum
"[...] whereas, by this present Constitution, which will be valid henceforth, now, and forever, We order and enjoin that nothing must be added to Our recently published Missal, nothing omitted from it, nor anything whatsoever be changed within it under the penalty of Our displeasure.
"[...] Therefore, no one whosoever is permitted to alter this notice of Our permission, statute, ordinance, command, precept, grant, indult, declaration, will, decree, and prohibition. Would anyone, however, presume to commit such an act, he should know that he will incur the wrath of Almighty God and of the Blessed Apostles Peter and Paul."
https://www.papalencyclicals.net/Pius05/p5quopri.htm
We only need to look at the counter church, today and for the 51 years, to see this very wrath upon her.
Holy tradition carries as much weight as written precepts, while at the same time, holy tradition stems from written precepts (as well as by word). The Tridentine Mass was substantially unchanged for approximately 500 years due to Quo Primum because the Church knew the papal bull's meaning and intention. The Lord God gave humans inference reasoning and logic to employ so we don't have the tedious and potentially limitless task of covering every interaction word-for-word in order to make something lawful.

Say it with me.
"nor anything whatsoever be changed."
Do even you know what whatsoever means? Here, let me help:
whatsoever
/wɒtsəʊˈɛvə/
(adverb)
at all (used for emphasis)
Did those other popes change
anything at all? Yes. Then by your moronic interpretation of Quo Primum, they broke the law. But, of course,
Papal Bulls do not bind future Papal Bulls. Where a newer bull contradicts an older one, it overrides it. See how it says "Our displeasure"? That doesn't mean the ghost of St. Pius V. That means the pope's displeasure. If you break the pope's law, you displease the pope. The pope's law can't break the pope's law. It's like saying a constitutional amendment can be illegal. The only way a law can be illegal is if a higher law forbids/contradicts it, but a Papal Bull is no higher than another Papal Bull. Pope St. Pius V understood that, and the meaning of that clause was never to say that other popes couldn't alter it, only that the lesser clergy couldn't. The point was to maintain liturgical uniformity, to avoid it being altered by patriarchs and bishops in their own regions.
If, somehow, Quo Primum was binding on the laws of all future popes, then all those popes who altered the Missal minorly would also have broken the law.
Because NO WHERE in Quo Primum, or any other legal docuмent of the Church, does it say the change has to be substantial. How hard can this possibly be to grasp?