Actually Matto, the teaching of the Church is quite clear; the sacraments are necessary unto salvation and the sacrament of baptism is not optional. This is the teaching of Trent and Scripture especially John 3:5 and Eph 4:5. This teaching is the common and constant teaching of the Church.
As an example of why I believe the teaching is not clear is if the Church has always taught that there was no BOD or BOB, why do so many of the Catechisms teach BOD and BOB? Why did so many saints believe in it? Why did even some Popes teach it?
Perhaps the truth is in the middle. No, the Church has not explicitly taught that there is no such thing as BoD/BoB. Clearly the Church has allowed the opinion among Catholics. At the same time, the Church has not actively taught that there IS a BoD. Consequently it's a matter of opinion and of speculation. Both sides that shout heresy are gravely mistaken. Those who call "Feeneyites" heretics are wrong, and so are the Dimonds who hold that anyone who believes in a restricted BoD for catechumens are heretics.
There's simply no evidence that BoD has been revealed.
There's been speculation on the subject and the opinion of BoD has been widely adopted.
But that doesn't make it dogma or infallible truth.
Trent taught the necessity of Baptism for salvation. After Trent, the BoD theorists such as St. Robert Belllarmine were careful to say that those who have BoD receive the Sacrament of Baptism
in voto, not that they are saved without it. That (arguably) preserves the necessity of the Sacraments for salvation. But I consider it to be very weak.
As I said, I have not EVER seen a theological PROOF for BoD. They simply SAY it exists.
St. Augustine floated what he admitted to be a speculation (and later retracted it).
Early Scholastics, in consultation with St. Bernard, adopted BoD (evidently not knowing about St. Augustine's retraction). St. Bernard replied that he would rather err with Augustine than be right on his own. (Sounds authoritative, eh?)
Then it took hold among scholastics, including St. Thomas.
After St. Thomas, due to his authority, it eventually spread like wildfire.
So where's the ultimate authority, a tentative speculation by St. Augustine?