God showed himself to the world multiple times, most notably between the years ~4 B.C. and A.D. ~30.
Even though God clearly revealed himself, many (most) still rejected him.
God could instantly materialize in front of everyone in the world and spell out “I am God and the Catholic Church is True.”
Guess what would happen?
Catholics would still be Catholics. Atheists would say it was a Government hoax, mass hallucinations, a super virus, or some other explanation.
Non-Catholic Christians would say it was the devil.
People would soon after forget. Nothing would change.