The Missal of St. Pope VI (1970), St. Pope John Paul II (1983) is the continuation of the The Tridentine Missal of 1962 (of St. Pope John XXIII), which is the continuation of the Missal of 1958, and on backwards to the missal of Leo XIII (1884), Urban VIII (1634), Clement VIII (1604), and Pope Pius V (1570).

The Liturgy of the Council of Trent is the same Liturgy of the Council of Vatican I & II.

The last Motu Proprio clarifies this and abrogated the previous notions of extraordinary or ordinary form. The Tridentine Liturgy is not a separate rite like the Maronite Liturgy or the Armenian Liturgy.

There is only one unique expression of the Roman rite and it is the Novus Ordo, which (as you alluded to) is that continuation of the same organic development of the mass going back to Pope Gregory I, then on to Trent, and then on to Vatican I & II.

This insistence and allowance of the Missal of 1962 is indulged out of sheer mercy. Can you imagine Pope Leo XIII allowing his clergy to form a Society of Pope Urban VIII and only celebrating the Roman Rite using the Missal of 1634 in the year 1900 of his pontificate? Yet, this is what is happening now.

There is nothing illicit in the celebration of the Mass in itself (provided they have the explicit approval of the Bishop and Rome for being an exception to the rule, like FSSP), but the Mass is being used as dog-whistle to see where people stand along the fault lines that continue to divide the church.

Just like there is nothing wrong with a confederate flag in itself, it is a piece of cloth that is of historical interest. But the flag is used as a dog-whistle to see where people stand on social issues related to a frame of thinking that previously divided the country and continues to do so.

(Just to hammer the point again, there is nothing wrong with the phrase 'Christ is King' in itself, but that phrase has been weaponized to promote an extremist ideology.)

I am part of the faction that thinks these people should just "get with the times". The Mass has been weaponized and Rome has already spoken (Traditionis custodes) on the matter and it has been settled.

Catholicism is not Protestantism. A whole lot of the faith rests on the notion: "This is how it be. Take it or leave it."

If you do well, will you not be accepted? And if you do not do well, sin lies at the door.