Whether and to what extent the V2 papal claimants are heretics is the wrong question, and it's a distraction from the core issue.
What matters is this and only this: Is the Conciliar Church the Catholic Church?
If Vatican II and the NOM had never happened, and we just had Bergoglio making heretical statements to Scalfari or on his plane pressers, it wouldn't matter. We'd rightly respond, as lay Catholics, that he's not our problem and that the Cardinals and bishops should deal with him. Cardinal Cushing was a blatant manifest heretic before Vatican II, and yet Catholics just carried on with their normal lives, going to Mass. At many points in Church history, probabaly 90% of Catholics didn't even know who the pope was.
We as Catholics recognize that the Conciliar Church lacks the notes of the One True Church founded by Christ.
As to how this happened, those are details ... whether it's because the See is vacant on account of heresy, whether it's partly vacant (sedeprivationism / sedeimpoundism), whether the V2 "popes" are being blackmailed and not acting freely, and that would render their acts null and void, whether Montini and others were drugged, blackmailed (for sodomy or pedophilia), or whether they were replaced by doubles (while the real Pope was kept in a dungeon), or ... my theory ... that Cardinal Siri was the true Pope (Gregory XVII) through his death in 1989, and then Ratzinger/Bergoglio after that were not valid bishops and could not exercise papal teaching authority (only bishops are part of the Ecclesia Docens). We can argue about whether Bellarmine was right or Cajetan or John of St. Thomas. While we could make our case, the Church has not defined the matter, so Catholics are free to believe any position.
People have accused me of being a dogamtic SV. I'm nothing of the sort. I'm a dogmatic indefectibilist. To attribute Vatican II and the NOM to the Holy Catholic Church is to undermine the Church's indefectibility ... unless you're engaged in the types of gymnastics where you try to assert that they're reconcilable with Tradition and most of the NOM aberrations are simply "abuses".
As for putting someone's name into the Canon, I could see someone who's a sedeprivationist making a case for doing so on the basis of his being in material possession of the office. St. Vincent Ferrer had an Antipope's name in the Canon for many years. Were his Masses sacrilegious, schismatic, or non-Catholic simply because he was in material error regarding the identity of the pope? Of course not. Would it have been a sin or schismatic act for the faithful (even those who were right about which was the true pope) to assist at one of St. Vincent's Masses? Of course not. You're making a mistake here in equating putting Francis into the Canon with a priest who would put Patriarc Kirill into the Canon as his bishop. Whereas the former is based on theological opinion, the latter constitutes formal adherence to schism.
Father Chazal undoubtedly puts Francis into the Canon, but he clearly does not adhere to the Conciliar sect, and it's no act of schism. He's basing this on his theological opinion (partly rooted in Cajetan and, mostly, John of St. Thomas) that Francis remains a visible sign of unity for Catholics based on his possession of the office (even though he lacks authority). Whether you agree with that or not, that opinion is tenable for a Catholic, i.e. is not heretical or schismatic.
Here even the radical SV Dimond Brothers did some excellent research regarding this issue, concluding that it's permissible for the faithful to assist at such Masses, showing where St. Pius V did not forbid it, re-admitting Anglican schismatics on the one condition that they not attend Canmer's Prot Rite (but permitting them to attend Masses of compromiser priests).