The Church has never taught that everything the saints say is definitive.
The Church has ALWAYS taught that the Pope and the Pope ALONE has the power of the Keys, which Our Lord gave to St. Peter, and by extension, to all the popes who would succeed him.
The Pope ALONE has this power, and it is only because the pope approves of the canons and decrees of Trent and all the other TWENTY Oecumenical Councils, that the Councils carry the note of infallibility.
Anything the pope ONCE CONDEMNS in regards to faith or morals (inclusive!) is condemned in eternity, that is, it is the revelation of God. The pope cannot condemn such a thing in error.
But there were no papal condemnations in Vatican II (the twenty-first Oecumenical Council), and this is emphasized by the Opening Speech of John XXIII, in which he said, no more condemnations.
He said the Church would now rely on the "medicine of mercy" instead of papal condemnation of error, but he forgot to point out that God's mercy is NOT MEDICINE. Therefore, "medicine of mercy" is NONSENSE. And yet, he was 'replacing' papal condemnation (the power of the Keys) effectively, with NONSENSE!!!
This egregious error has not been rectified yet, and it has been now 52 years running. And don't say that a 'real' pope cannot make such an error, because he was not defining nor was he condemning error. He was COMMITTING ERROR, and it was not protected by the Holy Ghost when he did so. This is how Modernism is so dangerous even for a pope.
Pope St. Pius X defined Modernism infallibly, and nowhere in his encyclical Pascendi did he say that the pope is in any way immune from Modernism. On the contrary, he said that Modernism would rise again, and it has the power to become the wreck and ruin of ALL RELIGION. That includes what the pope does and says.