"The Catholic Church itself is one of the biggest skeptics when it comes to miracles."
That depends on how you look at it. Every saint has his or her miracles. Did this nun actually have Parkinson's? I don't know. Was she cured of it by John Paul II. I don't know.
The church is wary of miracles in ordinary situations, but when they want to canonize someone, they always seem to find a miracle or two. They found some for Mother Theresa.
The thing is that all the testing for miraculous cures seems to take place solely within the Church.
This is incorrect. The apparently inexplicable cures are vetted by a panel of doctors and scientists, including non-Catholics and even the odd atheist or two (physicians in Italy are oftentimes freethinkers.)
You are misinformed.
Every saint does not have his or her miracle. Martyred saints don't necessarily have miracles attached to them.
Mother Teresa, no "h" in Teresa, hasn't been canonized, yet. Beatified, yes.
You are simply wrong. The panels who evaluate miracles according to seven strictly scientific criteria are composed of specialists in whatever type of disease is involved. They are selected for their professional competence and may or may not be religious believers--it doesn't matter. Their task is to review the before and after clinical evidence and to decide if a natural explanation can be found. All a miracle is is a cure that has no natural, plausible, scientific explanation. Miracle (miraculum) simply means "marvel" or "inexplicable happening."
That's a nice cuircular argument that there is no way out of. How do you know they "want" to canonize someone? Because they did?