Skepticism would have been unusual since there was relatively little data (about the inhuman size and scale of the universe) to undermine anthropocentrism.

Not necessarily — e.g. geocentric model was obviously wrong, but it was scientific and/or skeptical (or non-theistic, aka naturalistic) as it gets.

Egoism would have been reserved for the minority of top-dog theocrats who were corrupted and monstrified by their absolute power.

This is true only for the last ca. 6000–5000 years. Situation up until ca. 4000 BC was quite different.

The Birth of Civilization