Why don’t we understand that non-Catholics can be saved through “baptism of desire”?

Sorry, but that is not what the Church teaches. The Catholic Church doesn't teach that all who are saved are saved "through" or "by” the Catholic Church. It teaches that no one is saved outside the Catholic Church, that no one is saved without the Catholic Faith, and that no one is saved in a non-Catholic religion. You obstinately reject this dogma and therefore are not a Catholic. Your problem is not with us, but with the dogmatic teaching of the Catholic Church on salvation which you cannot accept.

Pope Gregory XVI, Mirari Vos (# 13), Aug. 15, 1832: “With the admonition of the apostle, that ‘there is one God, one faith, one baptism’ (Eph. 4:5), may those fear who contrive the notion that the safe harbor of salvation is open to persons of any religion whatever. They should consider the testimony of Christ Himself that ‘those who are not with Christ are against Him,’ (Lk. 11:23) and that they disperse unhappily who do not gather with Him. Therefore, ‘without a doubt, they will perish forever, unless they hold the Catholic faith whole and inviolate (Athanasian Creed).” Pope Gregory XVI, Summo Iugiter Studio (# 2), May 27, 1832: “Finally some of these misguided people attempt to persuade themselves and others that men are not saved only in the Catholic religion, but that even heretics may attain eternal life.” Pope Eugene IV, Council of Florence, “Cantate Domino,” 1441, ex cathedra: “The Holy Roman Church firmly believes, professes and preaches that all those who are outside the Catholic Church, not only pagans but also Jews or heretics and schismatics, cannot share in eternal life and will go into the everlasting fire which was prepared for the devil and his angels, unless they are joined to the Church before the end of their lives; that the unity of this ecclesiastical body is of such importance that only those who abide in it do the Church’s sacraments contribute to salvation and do fasts, almsgiving and other works of piety and practices of the Christian militia productive of eternal rewards; and that nobody can be saved, no matter how much he has given away in alms and even if he has shed blood in the name of Christ, unless he has persevered in the bosom and unity of the Catholic Church.” Pope Pius IX, Vatican Council I, Session 2, Profession of Faith, 1870, ex cathedra: “This true Catholic faith, outside of which none can be saved, which I now freely profess and truly hold…”

-Bro. Peter Dimond [Notice again how this heretic’s concern for baptism of desire is not because he believes that catechumens, that is, those who desire baptism, can be saved. Not at all. He wants baptism of desire to be true so badly because he can’t accept the Church’s dogma that all who die as non-Catholics are lost. He believes that souls can be saved in “false religions.” This is just another example which corroborates what I stated in the book, that for 99% of those who believe in baptism of desire, it means salvation for non-Catholics/salvation outside the Church.]