Is Buddhism polytheistic?
Buddhism doesn't take a particular stance; it's more a philosophy, and in the various nations it was exported to, it adopted the local gods.
Which is why, say, in China and many east Asian regions, people for the most part still believe in their ethnic religion and the gods of their traditional pantheons.
And the aforementioned of Shinto in Japan, and certain forms of Hinduism in India. Even the more "monotheist" forms of Hinduism are really more monist than monotheist, and still hold that many gods exist, albeit as facets of the Trimurti.
In addition, neopaganism is one the rise, particularly within the past 3 decades. According to various sources, there are between 500,000 and 1,000,000 Wiccans in North America alone, in addition to around the same number of other neopagan religions, like Asatru, neodruidism, Hellenism, etc.