Exactly. Making policy decisions now for what the world will look like in 600 years is absurd. Humanity has proven to be quite bad at making good policy decisions for the current generation, much less 5 or 10 generations from now.
I do think my original point still stands that we seem to be quite bad at making good decisions for more immediate generations. Considering our rather pressing current challenges (climate change, continued warfare, etc.) I'd settle for getting the next few generations in a better place before thinking about 25 generations from now.
For South Korea specifically, the population challenges are probably more immediate than other countries.