Catholics do not need to believe in these apparitions, but they have brought healings of body and soul to many.The Fatima apparitions are sketchy at best. The nice, tidy little story you get from websites and books, the one that makes it sound like a nice little fairy tale of Mother Mary appearing to some children is NOT what the actual recorded events and reports from the children themselves said and reported. Rome, once again, in the tradition of the False Decretals and the Donation of Constantine, has done some very serious editorializing.
Here is a good Orthodox take on Fatima: https://www.rusjournal.org/wp-content/uploads/2019/04/Fatima.pdf
Private revelations and apparitions of our Lady go back almost to the beginning of Christianity. St. Gregory of Nyssa (d. 394) tells of an appearance of our Lady and St. John the Apostle to St. Gregory the Wonderworker a century earlier (d.ca. 270). Our lady spoke to St. John, asking him to make known to Gregory 'the mystery of true piety,'.
More recently are the appearances to Juan Diego in Mexico of Our Lady of Guadalupe in 1531, which led to millions of conversions, appearances to St. Catherine Laboure in 1830 which led to the miraculous medal, and Lourdes in 1858 to St. Bernadette Soubirous, which led to many physical and spiritual healings.
Pius X said: "such apparitions or revelations have neither been approved nor condemned by the Apostolic See, but it has been permitted piously to believe them merely with human faith, with due regard to the tradition they bear."
Why all the concern and criticisms when so much good can come out of them?