Can you cite actual Catholic doctrine in support of this assertion? Leo X authorized trading indulgences for money -- was this not a "harmful ... practice" ? Honorius authorized (in a private letter, to be sure) the teaching of monothelitism. Was this not authorizing the teaching of a harmful doctrine?
Where in the decrees of Vatican I or any other ecumenical council do you find the assertion that a pope who teaches "harmful practices" is not a true pope?
(Besides, if “Francis” is a true pope, it is sinful and schismatic to question his decrees!)
It would be sinful and schismatic to refuse to obey his lawful decrees, but to question is not to refuse obedience. Again, where in actual Catholic doctrine do you derive the notion that it would be sinful and schismatic to even question the decrees of a true Pope?
If this is just your own opinion, then say so. But you shouldn't go around teaching your private opinion as authentic Catholic teaching.
Nor can we pass over in silence the audacity of those who, not enduring sound doctrine, contend that “without sin and without any sacrifice of the Catholic profession assent and obedience may be refused to those judgments and decrees of the Apostolic See, whose object is declared to concern the Church’s general good and her rights and discipline, so only it does not touch the dogmata of faith and morals.” But no one can be found not clearly and distinctly to see and understand how grievously this is opposed to the Catholic dogma of the full power given from God by Christ our Lord Himself to the Roman Pontiff of feeding, ruling and guiding the Universal Church.
As with post 9 I mean disciplines.
From https://novusordowatch.org/2020/07/on-disobeying-the-pope/
we read in this snippet some clarification:
Certainly the loving Mother [the Church] is spotless in the Sacraments, by which she gives birth to and nourishes her children; in the faith which she has always preserved inviolate; in her sacred laws imposed on all; in the evangelical counsels which she recommends; in those heavenly gifts and extraordinary graces through which, with inexhaustible fecundity, she generates hosts of martyrs, virgins and confessors.
(Pope Pius XII, Encyclical Mystici Corporis, n. 66)
…as if the Church which is ruled by the Spirit of God could have established discipline which is not only useless and burdensome for Christian liberty to endure, but which is even dangerous and harmful and leading to superstition and materialism.
(Pope Pius VI, Bull Auctorem Fidei, n. 78; Denz. 1578)
…[T]he discipline sanctioned by the Church must never be rejected or be branded as contrary to certain principles of natural law. It must never be called crippled, or imperfect or subject to civil authority. In this discipline the administration of sacred rites, standards of morality, and the reckoning of the rights of the Church and her ministers are embraced.
(Pope Gregory XVI, Encyclical Mirari Vos, n. 9)
The same holds true, of course, also for the doctrines that the Holy See issues in the exercise of the papal magisterium. Although not all doctrine comes with the guarantee of infallibility, nevertheless the teaching of the Pope is always guaranteed to be safe to adhere to, and always authoritative, for which reason the Church can demand complete submission of intellect and will to the Holy See in matters of Faith and morals:
All who defend the faith should aim to implant deeply in your faithful people the virtues of piety, veneration, and respect for this supreme See of Peter. Let the faithful recall the fact that Peter, Prince of Apostles is alive here and rules in his successors, and that his office does not fail even in an unworthy heir. Let them recall that Christ the Lord placed the impregnable foundation of his Church on this See of Peter [Mt 16:18] and gave to Peter himself the keys of the kingdom of Heaven [Mt 16:19]. Christ then prayed that his faith would not fail, and commanded Peter to strengthen his brothers in the faith [Lk 22:32]. Consequently the successor of Peter, the Roman Pontiff, holds a primacy over the whole world and is the true Vicar of Christ, head of the whole Church and father and teacher of all Christians.
Indeed one simple way to keep men professing Catholic truth is to maintain their communion with and obedience to the Roman Pontiff. For it is impossible for a man ever to reject any portion of the Catholic faith without abandoning the authority of the Roman Church. In this authority, the unalterable teaching office of this faith lives on. It was set up by the divine Redeemer and, consequently, the tradition from the Apostles has always been preserved. So it has been a common characteristic both of the ancient heretics and of the more recent Protestants — whose disunity in all their other tenets is so great — to attack the authority of the Apostolic See. But never at any time were they able by any artifice or exertion to make this See tolerate even a single one of their errors.
(Pope Pius IX, Encyclical Nostis et Nobiscum, nn. 16-17)
If in the difficult times in which Our lot is cast, Catholics will give ear to Us, as it behooves them to do, they will readily see what are the duties of each one in matters of opinion as well as action. As regards opinion, whatever the Roman Pontiffs have hitherto taught, or shall hereafter teach, must be held with a firm grasp of mind, and, so often as occasion requires, must be openly professed.
(Pope Leo XIII, Encyclical Immortale Dei, n. 41)
Wherefore it belongs to the Pope to judge authoritatively what things the sacred oracles contain, as well as what doctrines are in harmony, and what in disagreement, with them; and also, for the same reason, to show forth what things are to be accepted as right, and what to be rejected as worthless; what it is necessary to do and what to avoid doing, in order to attain eternal salvation. For, otherwise, there would be no sure interpreter of the commands of God, nor would there be any safe guide showing man the way he should live.
(Pope Leo XIII, Encyclical Sapientiae Christianae, n. 24)
Wherefore, as appears from what has been said, Christ instituted in the Church a living, authoritative and permanent Magisterium, which by His own power He strengthened, by the Spirit of truth He taught, and by miracles confirmed. He willed and ordered, under the gravest penalties, that its teachings should be received as if they were His own.
(Pope Leo XIII, Encyclical Satis Cognitum, n. 9)
They [the Modernists] will learn many excellent things from such a great teacher [as Cardinal John Henry Newman]: in the first place, to regard the Magisterium of the Church as sacred, to defend the doctrine handed down inviolately by the Fathers and, what is of highest importance to the safeguarding of Catholic truth, to follow and obey the Successor of St. Peter with the greatest faith.
(Pope St. Pius X, Apostolic Letter Tuum Illud)