What is canonization
The Catholic Church has its own customs, which have been indestructible for hundreds of years. One of such customs and traditions is canonization, that is, calling a specific person a saint, who lived and there is evidence of it, that she was special, she had an amazing connection with God and more – she worked miracles. This is not the case, however, that the Church can call whom she wishes holy. First you go through a long process of beatification and become blessed, if successful, and then only the canonization process begins. Some processes took hundreds of years. The Church is very scrupulous and skeptical about all reported miracles and gifts of a person.
Furthermore, there is also someone like the devil's advocate in the Vatican, who will do anything, that a person would not be ordained. The canonization itself is a solemn mass, which is led by the Pope himself. The last saint from Poland was John Paul II, that is, the former pope, A Pole named Karol Wojtyła. The key to holiness was the miraculous healing of a sick nun. Of course, many more miracles came to the Vatican, but this one did, that John Paul II became another saint. They are also popular saints from Poland: sister Faustina Kowalska, father Maksymilian Maria Kolbe, brat Albert, Saint Stanislaus, Queen Jadwiga and much more. It's worth reading a little more about them yourself.