It looks quite polytheistic, but it isn't. Nobody, not even the ones who pray to the saints regularly, not even the ones who pray to the saints exclusively, would claim that they are God. I imagine that it's much like the Loa in Haitian Voodun: you bring them your requests, and you venerate those Loa that you associate with, and that are appointed patrons over the things you care about. But you also understand that the Loa aren't God, and you know that the Loa actually answer to Bon Dye, who is the apex of the whole scheme, and the only perfect, and most powerful piece in the structure.
I am thoroughly protestant, but I have accepted certain Saints as my 'icons.' I don't pray to them, because I don't believe that's how it works. But I do respect their images and venerate them in my own private way, for the things that they have come to symbolize.