As a person in the pew, you and I don’t have to think it is a good idea or a bad one. The liturgy falls under the authority of the Holy See. I hate to be blunt, but they are not interested in what the man in the pew thinks is a good or a bad idea. They are interested in what is consistent with the scripture and the teaching magisterium of the Church. If something is consistent, then it is assumed by the Church’s authorities.
But the Church does this all the time. The prayers of the sacraments must be said in a very specific way. The prayers in the Liturgy of the Hours must be said in a very specific way. The prayers at the profession of vows of religious, must be said very specifically or the profession is invalid. The rosay must be said in a very specific manner or it’s not the rosary. I’ll give you an example from my own religious community. If we fail to say “our Holy Father St. Francis” and simply say “St. Francis” in the rite of profession, the vows are illicit and the rite has to be repeated to make it legal.
When you say that something is AS something else, you are making an analogy, not an equality. There is difference. The analogy here is that the plenary indulgence leaves you free of all culpability of sin, as you were after your baptism. Therefore, if you die in this state, you do not go to purgatory. Confession can forgive your sin, but justice requires that you purge the culpability in purgatory, even though you have been restored to sanctifying grace.
The Church has never said that the study of the diary replaces the study of scripture. She only says that the diary is consistent with scripture. Therefore, it is worthy of belief.
The phrase “the end times” is allegorical. It does not mean that the world is going to end shortly. The term was used by St. Paul, St. John and the prophets. The term refers to the fulfillment of God’s promise to save humanity.
If you believe that their writings contain private agendas, then you question the writer’s honesty. In which case you would have to question the Church’s infallibility when it declares these writings to be of the Holy Spirit and works of theology that contain the truth. We would have to question why the Church would declare so many mystics Doctors? A doctor is a Latin term for one who teaches truth. If someone like St. Teresa of Avila is a Doctor, she is a teacher of truth. Her writings cannot contain hidden personal agendas. Otherwise, the Church has made a grave mistake, a doctrinal mistake or a teaching mistake. But the Church allows us to teach theology from the writings of the mystics and to use them to better understand revelation.
If the Church believes that the request to celebrate Mercy Sunday on the Sunday after Easter, it is because it is consistent with the liturgical calendar and consistent with the faith of the Church. The Church prays as she believes and believes as she prays. Therefore, the content regarding Mercy Sunday was not a novel idea, but one that is consistent with what the Church has always believed but never included in its liturgical calendar. This happens all the time. We often add to our liturgical calendar, whether it be a saint’s feast day, an event or a truth of faith, such as God’s mercy.
It is our faith in Christ that tells us that what Faustina wrote and saw is legitimate. How do we know this? Because everything that she saw and wrote is consistent with Christ’s teachings about the mercy of the Father.
I hope this helps.
Fraternally,
JR