I mean, the Spartans aren't around now for the same reasons Korea has been a smaller population and size for its entire history.
Size matters. If the US was the size of Korea, which itself is as big as Delaware, WW2 would have been another story.
There is a lot to be said for 3 key factors...
Population size Geographic size/natural resources availability Education (which translates into proper utilization of those resources/political power/military power/technology)
South Korea has 1 of 3 of those going for it, and has done quite well for itself and will continue to do so, as long as it can turn all the now self-inflicted problems around.
North has 0 of 3.
Funny thing though, if the South's population, education and economy had the land of the North which is very very resource rich, they'd have a decent opportunity to overtake Japan in world economic power possibly rival Germany landing it in the top 3.
Good thing he's pro-universal healthcare, I'll need to get this hardon medically drained.