SSPX errors against Catholic faith:
-(1) They reject, by word and by deed, the penal efficacy of unjust excommunications. This cant be excused by appealing to alleged deficiencies in the CDF declaration, since they *preemptively announced during the consecrations* that *any censure* would have *no value.* That is precisely the logic that Clement XI and Pius IX expressly condemned because it would necessarily lead to ecclesial anarchy. Every heretic and schismatic is unjustly persecuted in his own eyes. Every heretic and schismatic perceives it as a crisis that the Church has condemned his errors.
-(2) They reject, by word and by deed, the supreme juridical authority of the Pope. They have reduced “The First See is judged by no one” to an empty formula. It is manifestly evident that they have relativized it in a way that robs it of its practical value in avoiding schism - the raison d’etre for the principle - and that is totally foreign to the understanding and praxis of the Church throughout its history.
-(3) They reject, in many and diverse ways, the indefectability of the Church. They teach that Roman Pontiffs and the overwhelming majority of the Church’s legitimate pastors have been “animated by a spirit contrary to the faith” for decades and that they have habitually abused their power to “kill everything” they touch - including the “sources of grace.” If their parallel ‘Church’ - which even they concede has not received jurisdiction in a visible, public, recognizable way - is the only part of the Church that gives life rather than death to its members, then the Church’s perennial teaching on indefectability cant be maintained.
-(4) They reject, in many and diverse ways, the disciplinary infallibility of the Church. They allege that a universally promulgated Mass is morally unsafe and positively harmful to souls. They reject the infallibility of the new canonizations using desperate and ad hoc reasoning - it is clear they only hold this position because they detest that the conciliar popes were canonized. But for their unwillingness to put effort into charitably interpreting a few ambigious texts in the Second Vatican Council in harmony with Tradition, I’m 100% certain all these guys would have agknowledged that the theological evidence against these positions is univocal and overwhelming.
-(5) They implicitly reject the perpetuity of the essential marks of the Church. They allege a dichotomous opposition between the “Catholic Church” and the institution they smear as the “modernist Church.” However, they claim to be in communion with and have (disingenuously) sworn obedience to a visible hierarchy that they believe to have been coopted by this “modernist Church.” Thus, they effectively deny that the visible, institutional Church pre-eminently and recognizably possesses unity, holiness, and apostolicity in the present age.
Each of these errors, taken individually, is far more serious than the doctrinal errors they allege concerning religious liberty or ecumenism in non-infallible teachings would be (especially if you set aside the extremely uncharitable hermeneutic thet they employ). Taken collectively, they amount to a wholesale rejection of Catholic ecclesiology by utterly trivializing all of the promises Christ made to his Church and robbing the Church of the practical authority and credibility that are necessary for its mission.
SSPX still don't realize that they're now in the same category as the Lutherans and Anglicans, because they only want the Catholic aesthetics without submission and fidelity to Rome.
Congrats on becoming Protestant!
The debate about sedevacantism becomes very clear when you realize that BOTH SIDES have to defend a Church. So often the burden is solely placed on the non-sede to defend their Church from a laundry list of allegations about how it is departing from tradition.
But the sedevacantist Church departs from tradition in ways that are far more numerous and radical - in fact, it is so obvious that it feels like pretense to refer to their ‘Church.’
Their Church has no visible unity, no hierarchy, no canonizations, no teaching office, no pope, no credible electors, no competent authorities to regulate the liturgy or determine the validity of sacraments, no marks of the Church, no ability to evangelize, defines itself exclusively by negating claims of the institution that is recognized by 99.9% of people as the ‘Catholic Church,’ no obvious path to restoring any of those things or even of getting to the point where it could even be recognized as a legal entity by any sovereign, etc…
Any Pope that tried to abolish any of those things would obviously be guilty of a far greater crime against the Church that any that are even alleged against the post-V2 popes by sedevacantists. And yet that is the ecclesiology they have embraced. It’s so insane.