"My point was merely that the act of imposing the doctrine would prove it wasn't a 'novelty'."
If it never was taught before, nor even disputed, then it would be a novelty.
"Such truths include the solemn canonizations of saints and the condemnations of Quanta Cura - and those who deny them separate themselves from the Church."
Not true. Denying that solemn canonizations are infallible would not be heretical.
It is heresy against ecclesiastical faith to deny the truth of a canonization.
The object taught by this formula includes all those teachings belonging to the dogmatic or moral area, which are necessary for faithfully keeping and expounding the deposit of faith, even if they have not been proposed by the magisterium of the Church as formally revealed.Such doctrines can be defined solemnly by the Roman pontiff when he speaks ex cathedra or by the College of Bishops gathered in council, or they can be taught infallibly by the ordinary and universal magisterium of the Church as a sententia definitive tenenda. Every believer, therefore, is required to give firm and definitive assent to these truths based on faith in the Holy Spirit’s assistance to the Church’s magisterium, and on the Catholic doctrine of the infallibility of the magisterium in these matters. Whoever denies these truths would be in a position of rejecting a truth of Catholic doctrine and would therefore no longer be in full communion with the Catholic Church.
The truths belonging to this second paragraph can be of various natures, thus giving different qualities to their relationship with revelation. There are truths which are necessarily connected with revelation by virtue of an historical relationship, while other truths evince a logical connection that expresses a stage in the maturation of understanding of revelation which the Church is called to undertake. The fact that these doctrines may not be proposed as formally revealed, insofar as they add to the data of faith elements that are not revealed or which are not yet expressly recopgnized as such in no way dimishes their definitive character which is required at least by their intrinsic connection with revealed truth ...
... With regard to those truths connected to revelation by historical necessity and which are to be held definitively, but are not able to be declared as divinely revealed, the following examples can be given: the legitimacy of the election of the supreme pontiff or of the celebration of an ecumenical council, the canonisations of saints (dogmatic facts), the declaration of Pope Leo Xlll in the apostolic letter Apostolicae Curae on the invalidity of Anglican ordinations... (CDF, Commentary on "Ad Tuendam Fidem")