The church of the devil is the world; it is all the carnality and evil to which fallen man is heir; it is every unholy and wicked practice; it is every false religion, every supposed system of salvation which does not actually save and exalt man in the highest heaven of the celestial world.
It is every church except the true church, whether parading under a Christian or a pagan banner. As Moroni will say in a later era of Nephite history, and as we shall ascertain in our evaluation of Rev. 18:1–24, it is ‘secret combinations,’ oath-bound societies, and the great world force of Godless communism. (Ether 8:14–26.)
(Bruce R. McConkie, Doctrinal New Testament Commentary, 3:551)