Please don’t take it the wrong way, but I groaned at seeing these amateurish arguments repeated.

1. The interpretation of the theologians of that passage of Vatican I is not the same as your interpretation. By it is not meant that there will be a Pope at every possible moment; if it did mean that, then we would not have interregna between papacies, let alone an interregnum that lasted for almost three years in the 1270s. I challenge you to find one theologian that understands this phrase as you do.
2. The argument that we will not be able to elect another Pope without cardinals is a silly one that seems to refuse to die. It is refuted by the writings of various theologians who address the question explicitly. See the following: https://wmreview.co.uk/2023/02/07/papal-elections-bellarmine/ https://wmreview.co.uk/2023/02/24/papal-elections-journet-cajetan/ https://www.wmreview.org/p/papal-elections-billot https://www.wmreview.org/p/papal-elections-without-the-cardinals https://www.wmreview.org/p/elections-victoria
3. While some Sedevacantists may fall foul of this condemnation, or come close to it, I do not, for I deny that the whole hierarchy has defected. I also deny that the ordinary magisterium has erred. In fact, it is for these reasons that I am a Sedevacantist. It is undeniable that what appears prima facie to be the Catholic Church has changed Her infallible and immutable doctrine on various questions (for example, on religious liberty, latitudinarianism, the death penalty, justification, collegiality, etc.), but we know that this is impossible. A vacancy of the Holy See solves these problems because an Oecumenical Council is not an oecumenical council unless it is approved by a Pope, and the infallibility of the ordinary magisterium flows from the Papacy, so that, if the Holy See is vacant, the teaching of the bishops taken as a moral whole can err since the definition of the ordinary magisterium is the teaching of all the bishops of the world taken together with the Pope.

I also find it ironic that the quote you have produced mentions unity of Faith, yet that which appears prima facie currently to be the Church most certainly does not have unity of Faith; one can believe whatever one likes about de fide doctrines to-day and still continue to be regarded as a Catholic, uncensured and unpunished, not only by the world at large, but also by the supposed authorities in each diocese and the supposed authorities in Rome. For the Church to have unity of Faith, Her members must all publicly profess the same de fide doctrines. Yet the supposed Pope himself does not do this: he has stated that Luther was ‘not wrong about justification’ (a position anathematised by the Council of Trent), that the death penalty is ‘inadmissible’, and that there is a right to religious liberty. Yet all these positions are directly contrary to teachings that must be believed with divine and Catholic Faith.

You have managed to divert our discussion away from admitting that I was right about the validity of Eastern schismatic confessions and that the exercise of jurisdiction is incompatible with heresy, as taught by St Thomas. I ask that you concede this as a matter of courtesy.