Lennier's Tears
Regular
The impression I got wasn't just that Earth was "sent back to the stone age" by a nuclear war but that the war itself created a reaction against technology and outside influence that's taken along time to fall away.
You could argue as well that we don't know that nobody did anything to help, maybe they did and maybe the non xenophobic population that survived moved off world with those who remained being from Daniels side thus unwilling to accept help or leave.
Yes, you're quite right. There is indeed apparently a strong anti-technology and anti-alien sentiment involved in the "great burn", and a great many people apparently really wanted to live like that. It's also true that we simply don't know what is going on with the population of Earth who do NOT feel that way. Maybe they are indeed elsewhere, leaving the rest of Earth alone to do their isolationist thing. And maybe there are some Rangers there to VERY gently guide those people back to interstellar travel and politics. I'd have to wonder WHY, though. And, after 500 years anti-technology sentiment would have turned into total ignorance. There could be quite a few generations in those 500 years, depending on just how anti-technology those people are, and whether they reject all medical science and thus significantly reduce the average lifespan ...
In all, there isn't enough information for me to claim that it is unrealistic, and anything I say could be refuted by a "well, maybe ...", and that would be as valid a theory as any. The only truth is that that bit just really doesn't work for me. I don't have to love every single scene in every single episode for this to be my favorite show