Socialists don’t see a fundamental difference between a king or church owning the means of production and a merchant/capitalist/whatever owning it, because there isn’t a significant difference. Adam Smith was observing truths on the nature of property ownership and how to increase the gains from such, not describing the idea of rich and powerful people owning property that would make them money by exploiting the value of labor. That idea is as old as agriculture.

Where it might get tricky is if the gains from owning the “relic” were funding welfare programs/charity more than they were funding the excessive lifestyle of the clergy, but that’s not something Catholics are particularly known for living up to, responsible usage of tithes and actually following the precepts of ascetism in the clergy.