After Fr Ker's biography of Blessed John Henry Newman, I want to commend to you the biography of Archbishop Lefebvre by H E Bishop Tissier de Mallerais. The book, and its English translation, are more than a decade old, but it seems to me to have a lot to say to our current ecclesiastical malaise.
As a biography, it is a finely detailed and balanced account of someone whom the author loved and respected, but with regard to whom he was determined to find out the truth. So one can find in this book a very 'conflicted' person. Sometimes he seems to be leaning over backwards to show proper deference to the Vicar of Christ; on other occasions, he seems almost sedevacantist (ET p 549 "the See of Peter and posts of authority in Rome being occupied by anti-Christs ..."; et cf ex gr pp 487, 506, 508). I do not see this inconsistency as unforgivable. The Archbishop was reacting to an ecclesial situation which has little parallel in the more recent history of the Church and accordingly has few guidelines provided for it in Canon Law and the Manualists. And the p 549 I cite in my parenthesis follows closely upon the Assisi Event; one can understand why the vision of the Antichrist, sitting where he ought not, as pagan idols did in the basilica at Assisi, should have been particularly vivid in Lefebvre's mind. But he remained firmly and resolutely opposed to the seductions of sedevacantism at a time when a lesser man might have sought its easy and 'logical' solution.
When there are dysfunctions in the institutions of the Church Militant, the problem is that the old markers, including the Rule-Book, do not, cannot, function in the same way that they are designed to work in 'normal' times. The history of earlier centuries does provide examples of behaviour, not much less uncanonical than Lefebvre's, which was subsequently validated by History. The Arian crisis, marked by widespread episcopal heterodoxy, is one example. The Avignon exile and the Great Schism of the West afford a veritable laboratory of confused crises in which tidy solutions were beyond the grasp of good men and eventually order was restored by untidy expedients. These were not neat solutions; but perhaps an openness to untidiness is sometimes the only sort of solution available to Christians in via.
But is it true that Marcel Lefebvre was faced with a situation of grave disorder? I think we can avoid just loudly shouting at each other about our own individual subjective judgements; instead we can simply consider objective, Magisterial decisions. Summorum Pontificum confirmed juridically that the Latin Church had lived for some four decades under the dominion of ... yes ... a lie. The Vetus Ordo had not been lawfully prohibited. Much persecution of devout priests and layfolk that took place during those decades is therefore now ... officially ... seen to have been vis sine lege. For this so long to have been so true with regard to the Holy Sacrifice of the Mass, which lies at the heart of the Church's life, argues a profound illness deep within the Latin Church. And that Big Lie was reinforced by multitudes of Little Lies ... that the Council mandated reordered Sanctuaries ... that the Council mandated exclusive use of the vernacular ...
So, I suggest, we can read Bishop Tissier's book as a narrative of how a good, but very often puzzled, man coped with the incomprehensible. And we can do this to our own benefit. Many Catholics find our present situation incomprehensible. As in the situations which Lefebvre faced, some Catholics may naturally feel inclined to act as though the rule-book does still apply (and so to treat the Church's current office-holders with the same obsequium as if we were still in the pontificate of S Pius X); on the other hand, others may discern the dysfunctions and ask their consciences what God expects of them by way of resistance, as many did during the Arian crisis and the Great Western Schism.
But I must express my own considered judgement by saying that the Church Militant, and her institutions, have not collapsed to the degree that many fear. Proper respect for the Roman Pontiff, despite all; and to the Bishops of the Catholic Church; are still our obligation. It is conceivable that graver deterioration may occur (again, vide the Arian crisis and the Great Western Schism): it has happened before without the Church's ultimate indefectibility being affected, so, in theory, it could happen again; but it has not happened yet.
But what about if it does? Frankly, I do not think it is is our Christian duty endlessly to be anxious about worrying contingencies. There are millions of these, and what eventually does happen will probably not be any of them. That's what happens in History. But ... OK ... I have just agreed that such things, theoretically, can happen ... they can happen because they have happened ... so: what did previous generations of Catholics do?
Both Councils and popes have behaved very foolishly in the past. What followed? Christian people kept their nerve and got on with everyday faithful obedience and, eventually, the disordered Council or the nutty pope or the barmy bishops were quite simply forgotten.
Time itself possesses a quasi-Magisterial status. The decrees for regulating the Jews of the Fifth Ecumenical Lateran Council are now simply matters for embarrassment. What was iffy about that Council, or about the Pope who presided over it, has disappeared or gradually merged into what one might call the Church's general background noise (dogmatic decrees and anathemas of dogmatic councils are, of course, a different matter). What was unhelpful in Conciliar texts or their consequences or their "spirit" ... and when, after the Ecumenical Council of Vienne, the Templars were being led out to be burned, they probably thought that was unhelpful ... Time has purged away; or will purge.
Take the long view. Never panic. Stick to the Sacraments. Read your Bible. Stay in Communion with the Bishop of Rome and with your own local bishop, however silly either or both of them seem to you to be.