I'm of the same basic opinion. The angels and demons are just variations on what has had interaction with humans, and their benevolence or violence toward our kind.

The Hopi Indian lore says the civilization has risen and fallen four times. They also believe the next fall is the last. I think these cycles of great civilizations and crashes may go back much further than just 12,000 years. They may extend back into a time the the geological activity of the earth has wiped away any evidence of the earliest advanced civilizations.

The legends we hear of lost civilizations like Atlantis are just from the most recent 'lost' civilization. Many of the 'stone age' relics we have found may be just remnants of the start of a new cycle, our cycle. Unlike the Hopi, I don't believe a future crash would be the last unless every last human were destroyed. If there are humans left the natural cycle of human existence from subsistence living to advanced society would begin again.