You cannot call all Protestants heretics. It just cannot be done. You have to remember ecclesiology has developed significantly since Trent. Our Magisterium is living, and develops organically. It is not dead and frozen in 1546
The quote I provided was from the Catechism of Pope St. Pius X,
a 20th century catechism. And what Pius X wrote did not begin at Trent. It is what the Church has always taught.
**Catechism of Pius X: **
14 Q. Who are heretics?
A. Heretics are those of the baptised who obstinately refuse to believe some truth revealed by God and taught as an article of faith by the Catholic Church; for example, the Arians, the Nestorians and the various sects of Protestants.
But we don’t need a catechism to tell us that Protestants are heretics. It is common sense. What is a heretic? A heretic is a person who denies a dogma of the faith. Protestant sects deny many dogmas of the faith, which makes them heretics. If Protestants are not heretics, then there has never been any heretical group.
Regarding ecclesiology, the following 20th century Catechism teaches us who belongs to the Church.
**The Catechism of Pius X: **
9 Q. State distinctly what is necessary to be a member of the Church?
A. To be a member of the Church it is necessary to be baptised, to believe and profess the teaching of Jesus Christ, to participate in the same Sacraments, and to acknowledge the Pope and the other lawful pastors of the Church. …
12 Q. The many societies of persons who are baptised but who do not acknowledge the Roman Pontiff as their Head do not, then, belong to the Church of Jesus Christ?
A. No, those who do not acknowledge the Roman Pontiff as their Head do not belong to the Church of Jesus Christ. …
13 Q. How can the Church of Jesus Christ be distinguished from the numerous societies or sects founded by men, and calling themselves Christian?
A. From the numerous societies or sects founded by men and calling themselves Christian, the Church of Jesus Christ is easily distinguished by four marks: She is One, Holy, Catholic and Apostolic.
14 Q. Why is the Church called One?
A. The true Church is called One, because her children of all ages and places are united together in the same faith, in the same worship, in the same law; and in participation of the same Sacraments, under the same visible Head, the Roman Pontiff.
15 Q. Can there not be several Churches?
A. No, there cannot be more than one Church; for as there is but one God, one Faith and one Baptism, there is and can be but one true Church.
18 Q. Why is the Church called Catholic?
A. The true Church is called Catholic, or Universal, because she embraces the faithful of all times, of all places, of all ages and conditions; and all peoples are called to belong to her. …
20 Q. And why is the true Church called Roman?
A. The true Church is called Roman, because the four marks of Unity, Sanctity, Catholicity and Apostolicity are found in that Church alone which acknowledges as Head the Bishop of Rome, the Successor of St. Peter.
21 Q. What is the constitution of the Church of Jesus Christ?
A. The Church of Jesus Christ has been constituted as a true and perfect Society; and in her we can distinguish a soul and a body.
22 Q. In what does the Soul of the Church consist?
A. The Soul of the Church consists in her internal and spiritual endowments, that is, faith, hope, charity, the gifts of grace and of the Holy Ghost, together with all the heavenly treasures which are hers through the merits of our Redeemer, Jesus Christ, and of the Saints.
23 Q. In what does the Body of the Church consist?
A. The Body of the Church consists in her external and visible aspect, that is, in the association of her members, in her worship, in her teaching-power and in her external rule and government.
24 Q. To be saved, is it enough to be any sort of member of the Catholic Church?
A. No, to be saved it is not enough to be any sort of member of the Catholic Church; it is necessary to be a living member.
25 Q. Who are the living members of the Church?
A. The living members of the Church are the just, and the just alone, that is, those who are actually in the grace of God.
26 Q. And who are the dead members?
A. The dead members of the Church are the faithful in mortal sin.
27 Q. Can one be saved outside the Catholic, Apostolic and Roman Church?
A. No, no one can be saved outside the Catholic, Apostolic Roman Church, just as no one could be saved from the flood outside the Ark of Noah, which was a figure of the Church.
The above represents the teaching of the Church with respect to ecclesiology, and no pretended developement can contradict it. True developement only adds clarity to what has always been believed; it never contradicts what has been previously taught.