Totally agree. The sspx failed here, because of bad logic. They were trying to avoid the Sede argument “Well, if the new rites are all doubtful, then there’s no pope.” Or something similar. No, sorry Sedes, life isn’t that simple.
But hindsight being 20/20, I’m darn sure that the sspx’s approach to the new rites was/is in some way affecter by their avoidance of sedeism. Which is also very stupid.
If +ABL and the sspx had taken an approach based on principles (ie new rite words and historical condemnations) instead of an emotional approach (avoiding Sedeism), all Trads would be in a better spot today.
The sspx would have zero doubtful priests. The sspx would’ve drawn a clear line in the sand vs the Indult. And the sspx would be closer to the (correct) Sede view in the matter (ie conditional sacraments). Tradition would be stronger for it.
Though I hold the Sede position, I concede you could make an argument for the doubtfulness of the new rites, provided it doesn't imply they came from the Church.
As an example, Bp Williamson went through a line of argument from a Canonist on why the Mass of Pope Pius V was not abrogated by the NOM, and not obrogated correctly (if I'm recalling correctly).
Source:
Lecture 38 of 63 — Matthew 16 Indefectibility & NOM — Wednesday, February 14, 1996
https://open.substack.com/pub/vladsarto/p/bishop-williamson-teaches-the-gospelBack on the topic of the thread, assuming John XXIII was a valid Pope (or even that these changes were made by Pope Pius XII, I'm not very familiar with it), a Pope would have the right to make the changes to the Mass. Pope Pius XII teaches this in Mediator Dei, para 58
58. It follows from this that the Sovereign Pontiff alone enjoys the right to recognize and establish any practice touching the worship of God, to introduce and approve new rites, as also to modify those he judges to require modification.