Is it realistic to think that humanity would give up all their technology?
You might think not... Romo says so at the end, and Adama says "You underestimate the desire for a clean slate, Mr. Lampkin". I think he's right.
People are misunderstanding slightly too... they arent going caveman... they just arent using computers and building tech heavy structures and things like that. They have their basic supplies and can make tents and things, they have whatever medical supplies remain for emergencies... they really aren't giving up all that much, because they didn't have that much. The only tech they are giving up really is the ships themselves, and they've been trapped in those things for the last 5 years yearning to see a blue sky.
It's not as farfetched as people think.