Re: Was the ending realistic?
I think that people are under the impression that when they "gave up their technology" they literally burnt everything.
My opinion is that they stripped the useful stuff out of all the ships and farmed it out amongst the various communities they set up throughout the world, which would gradually run-out or break over time and be unable to be repaired.
This would ease the transaction to becoming self-reliant, and living off the land.
"A perfect organism, unclouded by remorse, or human illusions of morality." - Ash, Alien