Some people prayed to Mary McKillop and recovered from their illnesses. Hence, Mary must be a saint/miracle worker. A lot prayed and did not recover. Is this how we establish cause and effect these days? Nonetheless, she clearly did some good work, as do so many who go unrecognised.
And since when has the Vatican operated on common sense and evidence? If sainthood were awarded on generosity and persistence in the face of adversity, say, there'd be fewer saints. But where's the PR aspect in that?