Taoism, Zen Buddhism, paganism, deep ecology, Native American religions, or forms of Christianity verging on pantheism such as Creation Spirituality. This pantheistic wave is fed by the destruction of nature and the earth proceeding all around us - the more we risk losing it, the more of us realize how deeply we value it. Many of us too are fed up with life-hating religions from ancient times that tell us that this earth is no more than a staging post on the road to heaven, and this body is just a cage for our eternal souls. Love of nature, and feelings of a pervasive divinity in nature and in ourselves, are possibly the strongest reasons why many people are attracted to paganism in the first place. I would guess that for most people the need for a religion that affirms life, the body, sex, nature and the universe is more powerful than the need to have a variety of gods to worship.
Polytheism comes later, if at all, and it is learned.
Many modern pagans regard Goddess and God, or gods and goddesses not as real literal entities with distinct powers, but as symbols or aspects of the one Divinity of nature, expressed in different forms in land, sea and sky. If you regard natural reality as divine, and learn to look at it in a different way, then you do begin to see a numinous quality not just in the whole universe, but also in many particular things - in the ocean, in mountain streams, in deer, in trees, in the sun. It's tempting then to personify the divinity of each of these. With enormous unified wholes like the sun, nature or the ocean, this is natural and harmless. They can be acknowledged as centres of numinous power without losing any of our ability to perceive each one of them directly.