Marian Devotee and Jack Common:
Florence taught dogma, but you have misunderstood that infallible truth.
The Magisterium is the sole authoritative interpreter of Tradition, Scripture, and past teachings of the Magisterium. And the Magisterium has taught that those who lack formal (or “external”) membership in the Church may still be in a state of grace and may still be saved. So we must interpret the teaching of the Council of Florence as referring to those who are culpably outside the Church, i.e. whose rejection of the Church is an actual mortal sin.
Pope John Paul II: “For those, however, who have not received the Gospel proclamation, as I wrote in the Encyclical ‘Redemptoris Missio,’ salvation is accessible in mysterious ways, inasmuch as divine grace is granted to them by virtue of Christ’s redeeming sacrifice, without external membership in the Church, but nonetheless always in relation to her (cf. Redemptoris Missio, n. 10). It is a mysterious relationship. It is mysterious for those who receive the grace, because they do not know the Church and sometimes even outwardly reject her. It is also mysterious in itself, because it is linked to the saving mystery of grace, which includes an essential reference to the Church the Savior founded. In order to take effect, saving grace requires acceptance, cooperation, a ‘yes’ to the divine gift. This acceptance is, at least implicitly, oriented to Christ and the Church.” [All Salvation Comes Through Christ]
“The universality of salvation means that it is granted not only to those who explicitly believe in Christ and have entered the Church. Since salvation is offered to all, it must be made concretely available to all.” [Redemptoris Missio 10]
Pope Pius IX: “Here, too, our beloved sons and venerable brothers, it is again necessary to mention and censure a very grave error entrapping some Catholics who believe that it is possible to arrive at eternal salvation although living in error and alienated from the true faith and Catholic unity. Such belief is certainly opposed to Catholic teaching. There are, of course, those who are struggling with invincible ignorance about our most holy religion. Sincerely observing the natural law and its precepts inscribed by God on all hearts and ready to obey God, they live honest lives and are able to attain eternal life by the efficacious virtue of divine light and grace. Because God knows, searches and clearly understands the minds, hearts, thoughts, and nature of all, his supreme kindness and clemency do not permit anyone at all who is not guilty of deliberate sin to suffer eternal punishments.” [Quanto Conficiamur Moerore, n. 7]
Non-Christians can enter the state of grace by a baptism of desire, then if their rejection of Christianity is not an actual mortal sin (due to invincible ignorance), then they remain in the state of grace. If they commit actual mortal sin in some way, they can return to the state of grace by perfect contrition. Therefore, they can die in the state of grace without converting to Christianity.