Church refers to the institution of a Christian religion as well as the building itself, mass being one of the various services performed there so OP is correct.

Edit. Also, by using "Church" OP doesn't limit the joke to just the Roman Catholics, there have indeed been cases of Religious Fuckwittery in other Parts of the Non-Critical Thinkers... pardon me... Religious groups and their numerous denominations.

This is called metonymy. Don’t try to be a language pedant if you don’t understand figurative language