Actually, the OLD religions in england and the germanic/french territories (Kelt and related areas) were an older form of polytheism -- basically a two-tiered set of animism and polytheism.
That's the well from whence all the pixies, sprites, brownies, trolls, and other demi-gods ... as well as the harvest/fertility gods come from.. the "lesser" gods. It isn't exactly like Shinto but there's some strong parallels.
Yeah, its very difficult to parse out all the Victorian insertions of fanciful religion but there are a number of real celebrations in Europe that really are hundreds and hundreds of years old if you trace them (though often very few are aware of the pre-christian roots). And yes, historians are routinely dismayed
The Golden Bough suffers mightily from 19th C. Victorian delusions about such things
so it has to be taken with lots of salt.
OTOH, its a *great* source for writing fiction like this (or using as a D&D source).