Fourth Lateran Council (1215): “There is but one universal Church of the faithful, outside which no one at all is saved.”
Pope Boniface VIII, Bull Unam Sanctam (1302): “We are compelled in virtue of our faith to believe and maintain that there is only one holy Catholic Church, and that one is apostolic. This we firmly believe and profess without qualification. Outside this Church there is no salvation and no remission of sins, the Spouse in the Canticle proclaiming: ‘One is my dove, my perfect one. One is she of her mother, the chosen of her that bore her’ (Canticle of Canticles 6:8); which represents the one mystical body whose head is Christ, of Christ indeed, as God. And in this, ‘one Lord, one faith, one baptism’ (Ephesians 4:5). Certainly Noe had one ark at the time of the flood, prefiguring one Church which perfect to one cubit having one ruler and guide, namely Noe, outside of which we read all living things were destroyed. … We declare, say, define, and pronounce that it is absolutely necessary for the salvation of every human creature to be subject to the Roman Pontiff.”
**Pope Innocent III (1198-1216), Profession of Faith prescribed for the Waldensians: **“With our hearts we believe and with our lips we confess but one Church, not that of the heretics, but the Holy Roman Catholic and Apostolic Church, outside which we believe that no one is saved” (Denzinger 792).
Pope Pius IX (1846-1878), Allocution Singulari Quadem: "For, it must be held by faith that outside the Apostolic Roman Church, no one can be saved; that this is the only ark of salvation; that he who shall not have entered therein will perish in the flood; but, on the other hand, it is necessary to hold for certain that they who labor in ignorance of the true religion, if this ignorance is invincible, will not be held guilty of this in the eyes of God.
Pope Pius IX The Syllabus of Errors: [The following are prescribed errors:] "16. Men can, in the cult of any religion, find the way of eternal salvation and attain eternal salvation. - Encyclical Qui pluribus, November 9, 1846.
“17. One ought to at least have good hope for the eternal salvation of all those who in no way dwell in the true Church of Christ. - Encyclical Quanto conficiamur moerore, August 10, 1863, etc.”
Pope Pius XII (1939-1958), Encyclical Humani Generis: “Some reduce to a meaningless formula the necessity of belonging to the true Church in order to gain eternal salvation.”
There are many and many more. I listed only few examples.
All just personal opinions? And the Council was not “Church” - in fact it erred?
I do not deny that but so far I’m not persuaded by your argument. Maybe you can shine a bit more light on the topic.