Easy for you to say, I just had a very angry Thor come round...seems I'd forgot to return his lawn mower...talk about a temper
You have to cut him some slack: lawnmowers are a bit of a Thor point.
i don't know much about Glorantha, but I do know that ancient Celtic religions were more closely in keeping with Animism than worship of particular gods. Although they did have gods (Oghma comes to mind) their druids, if I'm not wrong, seemed to be interested in nature spirits and placating them rather than adherense to deity based religion.
We know very little about Celtic religion, to the point that some people don't believe that there
was a single pan-Celtic relgion (in fact, there are some scholars who don't believe there were Celts). As far as we can tell, they worshipped gods in much the same way as their neighbours.
Druids were the Celtic scholarly class. They did everything scholarly: History, astronomy, poetry, law, theology, magic: the whole lot (though an individual Druid would probably not do all of it). Some
may have been Nature priests, although we have little or no evidence for that.
Many Celts, bear in mind, were reletively civilised urbanites: they weren't all savages by any means.
You can equally ascribe the rise and success of monotheism to its convenience for large scale autocracy.
I have two problems with this: first, that doesn't account for the nations that have practiced large scale autocracy and Polytheism very conveniently: Egypt, Persia, China, etc etc. Second, you are talking as if "Polytheism" and "Monotheism" are schools of thought with many shared characteristics. Persian polytheism had almost exactly nothing in common with, say Viking polytheism except they had more than one god: Christianity/Islam/Judaism have almost nothing in common with Aten or Sol Invictus other than that there is just one (or at least one clearly supreme and the others barely qualifying). Its like talking about "Paganism" as if its a religion. Paganism, and Polythieism/Monotheism, are types of religion each of which contain many examples that have nothing to do with each other at all.