Thats such a pretty topic. Still, it does feel like a mashup of Fallout and Fall From Heaven (a Civilization IV mod). But still, at least I think that what you are describing could be earth just just around 100BC.
People embrace their gods and carry on the stories unfolding during their gods... earth time to the next generation. These gods of course where pretty powerful, but somehow they were prone to fighting and cheating at each other, or going for a... ehm... date down to earth. Keep that impression for a moment.
Now fast forward to the point of your stories start. The next iteration of human rise and fall did start, but sadly these guys will have pretty hard time even coming to a second age of iron (because all the iron easy accessible was mined out centuries ago). Now they wander around, dwelling in wooden huts somewhere thousend years ago Germans and British Vacationists fought for the best chair at the pool. That area is now is a desert like area, because the Mediterranean Sea dried out, but at least there are no glaciers pushing forward downhills over here.
Its kind of cold, so they gather around a warm fire and start telling stories about the "old ones". You might hear the tales of Pot-Harald, who did beat a creature, shimmering in the sun, to death with his trusty broom while completely missing that he was parked in the friendzone by the red-haired lady he did like really. Or the tale of Mister Dom, who tamed a wild beast and used it to race other beast riders, until some day his best friend died. Or the tales of the well dressed guy which went out to fight the evil in the world while drinking huge loads of alcohol before grabbing the bad guys lady for a... walk. Hey, there are children around here!
Speaking of them; one might ask, what did happen to the old ones. Parents now start looking at each other and make space for the elder of the community, which - so tales tell - is old enough to know all the stuff he is telling first hand (weeeeell...).
So this old man places himself and start telling the story of the Old Ones, that worshiped the Apple of Awareness by carrying around small tokens with a picture of it, showing it slightly bitten off as a symbol for their own connection to Awareness and Wisdom.
But there were a mischievous group of baddies, who thought their God - the penguin machine - was far superior. Both battled for eternities, until one day, the Kraken of Information - Octogogolos its name - did awake from its slumber and took away the Old Ones connection to all their wisdom, angry that no one even thought about worshiping himself! For centuries the Old ones tried to please him by offering pictures of pretty girls with... less coth than advisable and cute kitten. But Octogogolos was way to angry to fall for more offerings any more.
Sadly by taking the knowledge away from the Old ones, they forget how to watch for the skies and missed that the minions of Eduard, the Space-Munky, started throwing mountains from outer space to earth. That wasn't even a bad scheme; the minions expected someone back home catching these mountains, because the old ones didn't look pretty any more. But with no one knowing how to catch them any more, they did fall at the heads of the Old Ones, crushing their homes, flushing away towns with water and causing general mayhem.
If you look out to the east you still can see such a mountain. In this days people try to get ore out of it, but its pretty complicated...
At least the kraken was pleased with all the water now flooding the earth, because he always needed it to keep himself cool...
"And what do we learn about this", the elder now asks. "Right: worship your fruits, because they are good for you, but forfeit the machines, because they will anger the kraken. But you can keep yourself save from him by sharing pictures of kitten and pretty girls with the cold water."
So... as said to the beginning, that did happen to humankind already I think. But now people start carrying around books of such misunderstood stories and think they are lessens from gods or stuff like this. And it will happen again; but the outcome may change based on what kind of story is passed to the people out there. Maybe there are groups, that still worship the penguin machines, or try to awake the kraken Octogogolos so it will give back the knowledge to humankind.
Its all about the stories, and who tells them. Always.