Every developed nation is barreling towards this fate. It's what end stage capitalism and 5 chaebols-in-a-trenchcoat as a government looks like.
The only thing preventing population collapse in the West is immigration. Any country that wants to maintain a particular ethnic majority is doomed.
So why is South Korea like this? Because of the demands of work, the government being beholden to the chaebols, the demands on women to both work, have children and largely be responsible for raising them without work suffering. There's a vicious cycle of entrenched misogyny and women essentially opting out of this system (ie the 4B movement).
Add all this up and you have a country that is bound for crisis after crisis. You cannot look at this current crisis without understanding the broader context.
The endless pursuit of profits will quite literally destroy a country if you let it.