I did a lot of study on the 7 letters. Eyeopening stuff. It is interesting to note that Thyatira is the Catholic and Orthodox churches, there is a reference to Jezebel. Jezebel represents paganism. All paganism religions worshiped a mother goddess and her child. Like Venus and cupid, Ishtar and Tammuz, of which Ishtar was called "the queen of heaven." Sound familiar? To make Christianity popular when paganism was outlawed, and all their temples and priest paraphernalia were brought in, they also brought in the pagan goddess and child mystery religion of Babylon, superimposing Mary and Jesus into the imagery. And like the pagan religions, the goddess is loved more than the child.
Sardis is the age of the Reformation and all those dead doctrines excusing sin. But some, like John Wesley did not stoop so low. I believe he is one who it is written "You have a few names even in Sardis who have not defiled their garments; and they shall walk with Me in white, for they are worthy."