Not all religions define god(s) as ultimate creators. Take Greek for example. Influencers of reality, but not the makers of it. Certainly more ancient and fundamental and powerful than Mankind and rare to directly interact with. The difference between Dreamtime early beings and Greek gods is very minimal and actually rather indistinguishable. That doesn't make Greeks Atheist or less polytheistic. The Dreamtime concept of these first emergent beings is almost identical to the Hindu pantheon that emerges from the Brahman as fractions of that overall whole that control various domains of existence. Dreamtime, therefore, is quite polytheistic, far moreso than it could be said to be Atheist.
The supernatural is out for some Atheists (like me) but not necessarily for all. I should never included it with the brackets in my attempt at a definition.
So you're revising Atheism to just mean, there is no Divine being. Does this mean that the Atheist just refuses to believe that anything beyond our power and possibly even extraterrestrial is possible? Or do Greek gods living in a place beyond Man's reach, simply having great powers we don't understand not really count as gods per-se? Would this make the Greek pantheon Atheist because their gods are not 'creators of the universe'? Is animism an Atheist religion because it believes in spirits and forces in nature having an underlying intelligence that drives what happens but doesn't try to explain an origin or name such spirits as gods, even though they perform the roles classically attributed to 'gods'?
I think what I'm trying to say is that there is no religion that is Atheist - it is its own belief system and it is classically based on the Scientific Method, choosing to rely only on what has been proven and so far everything appears to purely be cause and effect related with no intelligent intervention beyond the actions of those that are alive, which is just a more complex system of chemical interactions.
Not all Shinto/Dreamtime variants have any ancestor spirits. They have ancestors but they are gone now. It is more a "family history" remembrance and honoring. The ancient Egyptian's false door alter is similar.
Maybe not all, but classically, it does. And furthermore, if you ask Google, "Do Shinto practitioners believe in a god?" you quickly get this:
"
Shinto is a polytheistic
belief system involving the veneration of many deities, known as kami, or sometimes as jingi. ... According to Japanese mythology, there are eight million kami, and
Shinto practitioners believe that they are present everywhere."
Which makes it sound like at least for the majority of sects, Shinto is very polytheistic in nature. (This is a religion I'm not too greatly familiar with myself.)