A Church without Ordinary Jurisdiction is a non-Apostolic Church. Consequently, it is not the Catholic Church at all. Notice, Vatican I.
"3. So then, just as he sent apostles, whom he chose out of the world , even as he had been sent by the Father , in like manner it was his will that in his Church there should be shepherds and teachers until the end of time." https://www.ewtn.com/catholicism/library/first-vatican-council-1505
In just the same way as the Lord appointed Apostles whom He chose out of the world, in like manner it was His will that there should be shepherds and teachers who are sent till the end of time.
This does not mean that time ended in 1965. It means there will never cease to be at least some orthodox Catholic Successors to the Apostles. That is easily confirmed in the Oath against Modernism: "I firmly hold, then, and shall hold to my dying breath the belief of the Fathers in the charism of truth, which certainly is, was, and always will be in the succession of the episcopacy from the apostles." https://www.papalencyclicals.net/pius10/p10moath.htm
Same doctrine differently stated.
Want to read it in a Catechism? Here is that of Pope St. Pius X: "19 Q.
Why is the Church also called Apostolic?A.
The true Church is also called Apostolic because she goes back without a break to the Apostles; because she believes and teaches all that the Apostles believed and taught; and because she is guided and governed by their lawful successors." If She were not governed by Apostolic Successors, what we profess in the Creed would be a false dogma each time we profess it. That is an absurdity. The Church will have Apostolic Successors until Christ comes again.
Another issue for Sedevacantists - the Ordinaries are necessary to pass the juridical declaration that the See is now (allegedly) vacant.
Fr. Suarez states: “I affirm: if he were a heretic and incorrigible the Pope would cease to be Pope just when a sentence was passed against him for his crime, by the legitimate jurisdiction of the Church
. This is the common opinion among the doctors.”
So where is this legitimate jurisdiction to pass the juridical declaration necessary before electing a new Pope? Sedes need it, but don't have it.
Again, in deciding the question of whether it should be Cardinals or Bishops to pass the sentence, it is said the Ordinary Pastors need to pass judgment, "In the first place, who should pronounce such a sentence? Some say that it should be the Cardinals; and the Church could undoubtedly assign them this faculty, above all if it were established with the consent and decision of the Supreme Pontiffs, as was done for the election. But to this day we do not read anywhere that such a judgment has been confided to them. For this reason, it must be affirmed that, of itself, it belongs to all the Bishops of the Church. For since they are the ordinary pastors
and the pillars of the Church, one should consider that such a case concerns them. And since by divine law there is no greater reason to affirm that the matter involves some Bishops more than others, and since, according to human law, nothing has been established in the matter, it must necessarily be held that the matter should be referred to all of them, and even to a general Council. This is the common opinion of the doctors. One can read Cardinal Albano expounding upon this point at length in De Cardinalibus, (q. 35, 1584 ed., vol. 13, p. 2)." (32) https://remnantnewspaper.com/web/index.php/articles/item/1284-can-the-church-depose-an-heretical-pope