Let’s go with your last question first. All human beings in heaven are saints. There are other creatures in heaven, but they have never been human: angels, archangels, etc.
Why not proceed to a canonization? It’s really a matter of prudential judgment on the part of the Church. There was a time when there was no beatification. As I said above, we went from having no formal process to a very complicated one instituted in the 11th century, to one which was trimmed down a bit in 1917 and trimmed down again in 1983. In between that, popes have really done what they want. They abided by the process, ignored it completely or they have skipped one part and ignored another.
In the cases of Mother Teresa and Pope John Paul, the popes were so certain of their sanctity that they dispensed with the waiting period to begin the process. However, in both cases, there was such an uproar from one side of the Church, mostly the Trad side, that it seemed prudent to stop at beatification to let people get used to the idea and let emotions calm down. Beatification serves almost as a buffer. By requiring those two miracles and sticking to that, you calm people’s nerves. Those who are too fervent and those who are opposed can be equally disruptive to the life of the Church.
Just like in the case with St. Francis, people who knew Mother Teresa and Pope John Paul had conflicting feelings about them. Some loved them and some distrusted them. Today, we look back at someone like St. Francis and no one dares say anything against the man; but that’s 800 years later. In his day, some Catholics, including cardinals, hated him. When he was canonized without delay, the indignation almost brought down the Lateran. There was no Vatican yet. To add insult to injury, the pope sanctioned the building of a basilica to him. Those devoted to Francis was thrilled, while those who had now been forced to venerate him were upset. A new saint had been shoved down their throat and a lot of money was being poured into a great basilica.
Different popes have take different approaches. Beatification helps to give something to those who are devoted to the saint and it calms those who want to wait and see. But as you say, since the pope already believes that the person is in heaven, he can do as he wishes and the rest of us have to follow along.
A great example of this is the SSPX’s reaction to the beatification of Pope John XXIII and Mother Teresa. They have accepted it, because the Church says so. However, since their cult is not mandated, the SSPX stays away from it as if it were a hot iron. Then you have religious families like the Franciscans who have asked for permission to include Bl. John XXIII, Bl. Mother Teresa and Bl. John Paul in its liturgical calendar with no shame or hesitation. Once the Franciscan Liturgical Commission decided and the generals voted, 1.7 million Franciscans may no longer have an opinion on the matter. Francis has spoken. End of story. These Blesseds are to be included in the Franciscan Liturgical Calendar and life.
If they were not in heaven, it would be a sacrilege to allow a mass and a LOTH for Bl. John Paul and a feast day for him in any part of the world. One of his writings has been added to Matins.
There is a collect for him that can be used in both forms, OF and EF.
**O God, who are rich in mercy and who willed that the Blessed John Paul II should preside as Pope over your universal Church, grant, we pray, that instructed by his teaching, we may open our hearts to the saving grace of Christ, the sole Redeemer of mankind. Who lives and reigns.
Deus, dives in misericórdia, qui beátum Ioánnem Paulum, papam, univérsae Ecclésiae tuae praeésse voluísti, praesta, quaésumus, ut, eius institútis edócti, corda nostra salutíferae grátiae Christi, uníus redemptóris hóminis, fidénter aperiámus. Qui tecum.**
We would not pray this way if we did not believe in his sanctity. Lex orandi lex credendi.
Fraternally,
Br. JR, OSF