I always think of Mark 8 and other verses where Jesus was quite hard on people who need signs from Heaven when I see stuff like this or similar.
11Then the Pharisees came and began to argue with Jesus. They tested Him by demanding from Him a sign from heaven. 12Jesus sighed deeply in His spirit and said, “Why does this generation demand a sign? Truly I tell you, no sign will be given to this generation.”
All things work for good for those who love God, but Fatima stuff can be a bit too occult with secret messages and prophecies etc...
Nobody DEMANDED the sign at Fatima. It was freely given by God.
Therefore, your objection to it is misdirected and pointless.