Decaying rural areas happen in every country, throughout history, throughout time. It’s just how the world works.

The only reason it recently reversed in the US was due to COVID.

Second, many countries are modern in some ways and backwards in some other way. To label a country as modern or not is silly.

Here how it works: I build a porch today and my neighbor builds a pool. In 30 years, he builds a porch but I build a pool. If you cherry pick porches, I look outdated and he looks modern, but it’s reversed if you cherry pick pools!

Japan has seen millennia of huge cultural shifts. Its strength is its ability to adapt and survive with some measure of continuity, even while embracing the new reality. Go watch some Ozu films. They're all about the "hollowing out" of traditional small-town lifestyle and culture. It isn't so much a problem as a feature of the landscape that reminds people about how transient their reality can be.

Additonally, most foreigners who would comment on HN or Reddit are earning significantly higher than the average Japanese or even Tokyoian.