Doug,
It seems to me that we get into deep and tangled discussions by mixing up terms. You discuss priests/magicians as if they were the same thing and then put in animism into the mix and shake to get shamanism. The dispute about “intellectualism” is somewhat misleading and mostly about semantics rather than substance. The need to “explain” natural phenomena and to try to control them and diminish uncertainty is probably the basis for the origin of religion. The essence of religion is belief, so that no one is stating that Egyptian priests did not ‘believe”. However, as societies evolve and get to be states you get, full-time practioners and they begin to develop a more coherent, and yes “intellectual” world view. Think of the amount of intellectual thought of an Aquinas, who was also a believer. It is not either/ or.
First, let’s clear the evidential bush. We have no direct evidence that “Egyptian priests were just following and expanding the beliefs and practices of the precursor settlers of the Nile Valley [my paraphrase]” If there is, all of us would appreciate a reference we can check. Thus, what we can do is to go by analogy. The settlers that returned to the Nile Valley after the dessication of the Sahara in the late Holocene were not hunter gatherers. The Sahara dwellers had become cattle herders about 6000 BC and abandoned the hunter-gatherer lifestyle. If you read the literature on shamanism (or the paper I quoted by Winkelman), the characteristic religion associated with a hunter/gatherer lifestyle is shamanism. What has happened, except in the New World, is that when societies abandon this lifestyle for pastoralism and/or agriculture they develop other religious practices.
Although all groups with shamanism are also animistic, not all animistic groups are shamanistic.
Malinowski proposed a scheme that I have found very useful in a heuristic manner. Even though I’ll describe them separately, in real life societies use both, for example. Egyptian medicine used both empirically derived remedies as well as magical treatments. Both science and magic are attempts to control the world, but they differ in that science only deals with the natural world and natural causes while magic recognizes both natural and supernatural causes. Religion resembles magic in recognizing the existence of the supernatural, and differs from both magic and science in that the role of humans is that of suppliants rather than actors. The level of complexity of a society will also influence the mix. Smaller, less complex, groups will tend to have more magical approaches and mediums, sorcerers/magicians as well as herbalists. As the society gets more complex you begin to have more priests and organized religion with a hierarchy.
Would it be useful to look Egyptian religion with these points in mind?
Bernard