I think most temporal daydreaming is harmless, of course, but I actually think there is a bit of danger in idealizing a time period (usually when there are calls to “return” to it) without acknowledging the flaws that the time period had. Sure, we should take the things that worked in the past, but we should leave the things that didn’t.

Although, as a fantasy writer, I spend an inordinate amount of time dreaming about life in a pseudo-medieval society, I never lose sight of the fact this is a fantasy, and in a real medieval society I’d be pretty toast pretty fast (I doubt I would’ve made it to be as old as your average life expectancy for a peasant…). There’s that, and the realization that even in the fantasy stories I write, life pretty much sucks for the characters. I mean, the average life expectancy of a hero in an epic struggle between good and evil isn’t all that awful long either…