There's a lot wrong with this.

new nuclear plants are politically untenable now

Was the case but not so much now, especially as rising prices and inflation are crunching families. Several parties now include at least reviving shut-down plants that are safe to do.

the grid infrastructure isn’t good there

Could you elaborate here?

When the sun stops shining, it stops shining for the whole country

We're not that small, even going on the main islands alone.

When the wind doesn’t blow, it doesn’t blow for the whole country.

And this is just plain wrong for a number of climate and geographical reasons.

I've lived in Japan for more than a decade both in greater Tokyo and rural Tohoku in addition to traveling all around it.