No, It wasn't realistic at all.
Ron Moore fanboys keep using "Duh, all their technology was falling apart" as an excuse. They fail to realize even with the basic machine tools they had, they would have easily been able to setup a primitive industrial society. With those primitive tools, they would have been able to make more refined tools, and so on. Instead of 150,000 years, it could have been a few hundred years of development. All their knowledge of the mistakes of the past could have been remembered. The "cycle" could have truly been broken.
Instead they descended into neo-ludditism, which basically guaranteed that most of them would die from disease and starvation. How anybody believes giving up pretty much all your knowledge and history* is "making a clean break" is beyond me. It's running away from your past and dooming thousands of people to death.
* You would think that their history is something would probably want to remember, so that they don't make the same mistakes again, but then again this ending was monumentally retarded.