The Pope is the principle of the Church’s visibility.
I'm surprised to hear you say that-- but you haven't thought very clearly, since this harms your case more than makes it. The visibility of the Church is a bond of faith and charity. The pope is the principle of this visibility. If "the pope" neither has faith nor charity (we know he does not have the faith, and without faith it is impossible to have supernatural charity) then your "pope" doesn't amount to a hill of beans, he's a principle of disunity, not unity.
Neither are traditionalists subject to him in faith (as they don't share his faith) nor in charity (they are not subject to his laws).
So, can you explain again just how this principle of unity who has neither faith nor charity, and with whom traditionalists are neither united to in faith or charity is so important?
Sedevacantists end up with an invisible Calvinist Church composed of believers spiritually “subject” to illicitly consecrated bishops of questionable validity,
Just which sedevacantists are "spiritually subject" to "illicitly consecrated bishops of questionable validity"?
Are you even a traditional Catholic? There are no major concerns with the validity of any traditional group, but even if there were, it pales in comparison to the Novus Ordo which has been producing almost certainly invalid bishops and doubtful priests (who are likewise almost certainly invalid if ordained by a "new" bishop) since the late 1960's.
And if we take traditional Catholics as a whole, the group which most offends what you have mentioned are the SSPX faithful, who view +Fellay as their "lawful superior" or something along those lines.
And, traditional Catholics are hardly invisible.
giving no adherence to anyone other than themselves,
Excuse me? There is a reason that the main publishers of sedevacantis tracts cite copious sources to docuмent their position: the saints, popes and theologians have laid down the principles for their position, and sedevacantists merely apply those principles to the current situation.
There is likewise a reason that sedeplenists either quote themselves, SSPX "theologians" or a primary text which they don't understand.
If there was a pope, sedevacantists would certainly submit to him. It is their cognizance of the necessity of submission to legitimate authority which compels them to take the position they do in the first place, rather than simply give vain lip service.
since they have constituted themselves judges of the Supreme Pontiff,
No, they haven't. That is your obstinate misunderstanding. The "pope heretic" is already judged, this is the opinion of St. Robert Bellarmine and most others. Do you think Bellarmine constituted himself judge of the supreme pontiff? It's precisely
because the pope has no judge that Bellarmine taught as he taught, and that sedevacantists believe as they believe you silly woman.
forgetting that as a Catholic, one is obligued to believe there is a hierarchical order to everything.
But he's not compelled to actually ACT as if there's a hierarchy, right? He can judge all the laws and decrees of the hierarchy, rejecting them left and right as if the authority behind them was no more than a gentle suggestion from a subordinate.
Sedevacantists believe in hierarchy. That's why they consult the authorities on the issues.
It is a defined dogma of the Catholic Church that no one can be saved who is not subject to the Roman Pontiff. It is one of the requirements for salvation.
Pope Boniface VIII, in 1302, infallibly declared in his bull, Unam Sanctam: “We declare, say, define and pronounce, that it is wholly necessary for the salvation of every human creature to be subject to the Roman Pontiff.”
Which presupposes that there
is a Roman Pontiff in the first place, unless you believe that anyone who dies during an interregnum goes to Hell because a pope had not yet been elected when they died.
Also, many Catholics didn't even know who the pope was throughout history. Peasants, especially. "Subjection to the Roman Pontiff" is expressed by being subject to his laws and teachings, not by putting a picture of him in the hallway and disobeying everything he teaches and ignoring his laws.
Modern day donatists, fueled by mutual hatred for one another,
Hilarious! You don't even know what that means, or you haven't understood a single argument levied in favor of the
sedevacante thesis (probably both) to say that.
You are a prototypical example of an indoctrinated SSPXer who has bit into the whole "sedevacantist boogeyman" story. You probably sit around a campfire with a flashlight and tell your kids that if they're not good, the big bad sedevacantist is going to snatch them up and carry them to Hell, laughing maniacally. Pathetic.
sedevacantists divert the attention from the real enemy: Modernism.
So, in rejecting the authority of modernist non-Catholic heretics, sedevacantists distract from the modernist enemies. Gotcha.
Many sedevacantists, resentful and wounded (with reason), blame every single modern evil on the "usurp" of the conciliar Popes,
No they don't, but even if they did, that is hardly a distraction from modernism any more than blaming Stalin for communism is a distraction from communism.
losing focus on what the fight is really about.
You don't actually say what this is. Is it a contest to see how long one can hold mutually exclusive truths? If so, you win!
Satan and his many disguises: In present time, Modernism (the synthesis of all heresies).
Yes, one of them is as "the pope."
Instead of attacking the Modernist heresy that has infiltrated the Church, they use it as an ally to justify their own position.
Would you prefer they make a deal with the modernists and "change them from the inside?"
What is worse, there is no solution to sedevacantism.
Sedevacantism is a diagnosis, not a remedy. You only betray your complete ignorance on what you're arguing against, as if Fellay or Pfeiffer themselves are slipping you notes under the table.
Without a functioning hierarchy, the Church will never be able to choose a new Pope.
Ha! You think the Novus Ordo has a functioning hierarchy?
The Church is a perfect society and can always elect a new head. Many theologians have treated the issue of extraordinary elections, and you have been told this many times.