Is there an explanation in the text here?

I don't think South Korea's falling birth rates are a big mystery though... everyone, but especially younger Koreans are expected to work super long hours at their jobs, and housing is both expensive and pretty cramped (relative to Western houses, etc).  It's essentially too hard and too expensive to raise kids right now.

Web monetization.  Working on gfam.live to help creators earn from their content.

Do Koreans view it as an existential issue to solve?

A population isn't a monolith, but I'm sure lots of people are concerned... but solving this problem requires a bunch more housing to be built and a complete change in work culture and work/life balance.  Neither will be quick to implement.