Thanks for the question.
I have a different take on Dr. Marshall than Eric; I think Dr. Marshall is a liturgical purist, in other words, he only advocates for the TLM. He doesn't like the Novus Ordo at all, but I don't see him going so far as to consider Catholics who don't attend the TLM as non-Catholics.
In my opinion, he is not that exclusive about Catholics, only about the liturgy. I think that case could be made about many in the SSPX, but still not all those in the SSPX.
Pope Francis seems to have predicated his Traditionis Custodes on the notion that there is this total exclusivity among TLM advocates that has formed a type of practical schism in the Church, but the many responses from Bishops, Cardinals, journalists and faithful Catholics disabuse that notion and contradict Francis' assertion. This is an unfortunate moment in the Church.
Marshall does wield a good argument when he makes a case for whatever theological position he takes, so he is valuable to listen to if you want to hear all sides. In my view, I think that the TLM should be available to all who want it, the Novus Ordo as well, but the Novus Ordo needs to be cleaned up a bit too — far more abuse happens there, than at the TLM.
I think we are best served as a (both/and) Church; when we use all liturgies rather than consigning all to only one liturgy. We have many different rites within the Church, and each has its own liturgy. We have never been that exclusive as a universal Church, so now is not the time to pick on one sub-set of faithful Catholics. What we should be doing is cleaning up all the abuse in the Church by wicked prelates who continue to bring shame and scandal to the Church.
Much of Vatican II is beautiful and enriching. The teaching on the role of the laity, the Blessed Mother, and the universal call to holiness are worth proclaiming. It was meant to be a pastoral council and not intended to teach any new dogmas.
There are some points in a few documents that have been theologically challenged and, as a result; there has been controversy, confusion, and division. The Church would be well advised to clear up the confusion and eliminate the ambiguous parts, but based on Francis' track record, I don't see that happening any time soon.
These contestations will not cease until the Church does its job, but sadly I think many modernists have infiltrated the Church and they are content to keep the confusion going.
The official teachings can't change, but modernists are trying to present their false teaching as true, and they gain traction when the Magisterium does not clear things up. It becomes a kind of tacit "approved doctrine" because no one is challenging their false teaching with any force, (i.e. anathemas).
The issues pertaining to Vatican II have to do with several passages that have been misused, and are a source of contention for traditionalists like the FSSP, SSPX and others.
Those issues have to do with the statements on religious liberty, collegiality, attitudes toward non-Christian religions and a few other matters, not to mention the liturgy.
The problem is that when the statements are put out there that modernists can use in a non-authentic way, nobody clears it up. This is wrong, and the Church has a moral obligation to fix it.
Look at what Pope Francis did with Amoris Laetitia, he made statements that opened (albeit through footnotes) the door for Communion to be given to divorced and remarried Catholics (and, for that matter, theoretically practicing homosexuals could also receive), and when four cardinals (the Dubia) asked for clarification — he blew them off. Still, to this day, there has been no response.
When the Argentinian bishops followed up on Amoris with their statement justifying the practice of giving Communion to these groups, Francis in effect said they got it right and nothing else needed to be said on the matter.
The Church has a moral obligation to clear up these points that are raised and seem ambiguous.
- So when the FSSP or SSPX are told to give 100% assent to Vatican II or else, don't they have a right to ask for clarification on matters that may have been sketchy?
This is why we must pray for the Pope, the Bishops and all our clergy.
- Can a Catholic be a traditionalist Catholic and support the TLM without denying Vatican II?
Sure, you can be a Traditionalist without denying Vatican II, but you have a right, as a Catholic, to demand clarification on points that are not clear and may even seem to contradict previous teaching.
That is the moral obligation of the Church: to clarify.