I have wondered this and here is the answer I came up with. I am Christian and Druid at the same time, but love to study Wicca as well.
When you do some comparison of the "notes" of Christianity (monotheism) and paganism you find that in paganism, the God (male deity) usually resides in the heavens, as the Sun God, or such. The Goddess is usually an earthbound deity, like Gaia. To cross reference this to Christianity (monotheism) you find that Christ is the Heavenly Deity who comes to earth to interact with the Goddess, who resides upon earth. Together they form new life in the souls of mankind, along with making the earth a living and breathing, healthy place (supposed to anyway). And who in Christianity is "the Goddess"? - well for me that is obvious - Christ's Bride, the Church (genuine believers, not the hipocrites) has the position of Goddess because the God marries his Bride, the Goddess, and in christianity, Christ marries his group of genuine believers, making them "the Bride/Goddess". So While the Church is many people it is "one" organization that forms an entity of "Goddess". In this monotheistic faith, they will marry at the "marriage supper of the Lamb" (i.e. Christ). In Paganism, this is the "Great Marriage" - Christians expect this in the future, but do not call it the Great Marriage, but that is essentially what it is.
On Pantheons and monotheism: if you read Genesis 5,6, and 7, you find that it states clearly that since the days of Adam the "Sons of God" (heavenly angelic beings) married with the daughters of earth and that their children became the "men of renown, heroes of old", Noah obviously being one of these, which is why this is mentioned in his story between his patriarchial geanology and the rest of the story (apparently Noah's mother was a descendent of the Heavenly "Sons of God", and Noah had a divine and human heritage, making him a hero of old, a man of renown). These offspring of "Sons of God" and earth women became what we now call gods and goddesses/pantheon deities, and had real supernatural powers. The "Giants" (nephilim) are also mentioned along with "mortal men". Therefore there were three groups in those days, Angelic beings, whose offspring were the heroes and renoun men of ancient times/pantheon of gods and goddesses, Giants, and mortals. The flood only wiped out the mortals and maybe the giants, according to the Genesis account. The pantheon remained and no mention is made of the Giants. Noah and his family (the pantheon of gods and goddesses) remained...They had miraculous powers and were semi-divine...doesn't this strike you as the first pantheon in our era? Everything prior to Noah died...he and his half-divine heritage continued and his descendents remembered his mountain top dwelling place that functioned also as a temple (he made a sacrifice at the ark)- sounds like the Greek Mount Olympus or the Mountain where Valhallah existed, doesn't it-where gods lived and sacrificed at the same time? and for those cultures that think the pantheon resided underwater, like Atlantis, or on an island, well Noah's dwelling place "did" exist in those places depending on the stage of the story, for the ark was on/under the water, and on a mountain top surrounded by water for a time (an island). After the Noahide story, the Tower of Babel happened, the languages divided and the supercontinent (Pangea) divided into many (during the time of Peleg, says the Bible) - so it makes perfect sense that people remembered this pantheon of semi-divine humans who lived under the water, on an island or on top of a mountain top in different languages, which is why the pantheon deities have different names depending on what language/culture you speak of them in, even though they have basically the same functions. While Noah never forgot the "All-Father", his descendents did, remembering only him and his supernatural family, who I suppose formed the Atlantean society when they first resided on a mountain-top island surrounded by mists, and using miraculous powers. By the way, for info, the word "god" in hebrew, with a small "g" means "ruler, magistrate, governor, priest, king, heavenly messenter and sometimes idol". Noah had all these positions over his descendents, making him a "god" (small g), but not a "God" (big G). The word "God" (big G) means self-existent, uncreated being who brings salvation, i.e. the logistical first being who created all other things (all cultures, even pagan ones, believe this being had to exist logically). God told Moses in Ex 3:13 that his name is YHWH (Jehovah) which means "all saving being" - one who saves the day in all circumstances. Jesus' name means exactly the same thing which is why Christians believe that God and Jesus are "one" and the same, but "triune" with the Holy Spirit.
I personally think that it makes sense to worship ONE God, who came to earth as Christ, and is betrothed to his people (genuine believers in him), and will marry that group, making it his "Bride/Goddess". Together they will bring new spiritual life to other people, and restore the earth to it's original beauty. I also think that the pantheon is not mythical, but historical, and that instead of the pantheon being above us, we are descended from it and are actually a part of it /equal to it- you are a god or goddess by your genetic descendency from that group, and will become "The Goddess" if you choose to be part of the "Great Marriage" at the Marriage supper of the Lamb (i.e. Christ). The Egyptians revered Lambs as the highest deity as well, not just the hebrews or Christians, so this is a pagan idea as well as a Judeo-Christian idea.
For me this "theology" teaches me that I can be Monotheistic towards God with a "Big G", while revering my ancestor gods and goddesses (little g), and recognizing that I am one of them and have the same supernatural powers they had genetically. Because of my relationship with Christ, who said that if I believe in Him, I will have "more" power than he had while on earth, I can super power my Magickal/miraculous abilities, and can look foreward to becoming his full fledged Bride and Goddess at the Great Marriage which is predicted in Christ's own teachings.
Any way, that is how I look at it, and so for me personally, I am a monotheist who believes in a very real, historical and supernatural pantheon of which I am a descendent. Instead of worshipping the Goddess, I feel I am in the Goddess position, and must ask myself, "what do I do with that position for my God and Lord?" Your response to this would be interesting, as I know of no one out there who has thought of this as a religious system...
