Who's to say the ancient peoples were 'simple'? Are we so arrogant as to assume we are so much more 'enlightened'?
While we have indeed gained much scientific and technological knowledge, I believe we are fooling ourselves if we think we are superior because of this knowledge. I believe it highly probable that mankind's overall intelligence has actually diminished over time. How do we account for all our unused brain matter? I think there are many facets to one's intelligence, and that having scientific or technological knowledge is only one of those facets. Think of some of the mysteries of the world......how were the Pyramids built? how about Stonehenge? we conjecture, but no one knows for sure. But it's pretty obvious that people back then weren't dummies.
I don't think the Israelites, or any of the other peoples of the Bible, were 'simple.' At least not in the way that the term is being used.
And, in reference to someone's comment about believing in something or someone that we don't fully understand, and how absurd that seems---I think that's actually not too wacky a thing. I kinda like some mystery. Mystery adds spice to life. If I knew everything about everyone and everything, it'd be kinda dull. That's why God is so cool....it'll take eternity to really get to know Him, and His ways, because He is an infinite being.