saywhatnowman
The top comment here is a person who has had the unfortunate experience of realizing that their cultural and genetic family are at high risk of being trimmed away from the tree of life. That's a pretty serious existential dread to swallow. Have some sympathy for them.
I mean, if all of humanity were going extinct could we say something like "well, at least there's a good chance that squids will evolve sentience someday so we will live on through squidkind no reason to panic" and make you feel better about it? And if that worked, maybe we ought not to even worry about the entire solar system being wiped out since there are plenty of other solar systems (no need to be such a xenophobic solist). And if that made you feel better maybe we ought to not mind the whole galaxy being wiped out because ... and etc... etc... c:
Japan is more than a piece of land, or a group of people who make television programs and video games for you to enjoy. They are many millions of families each with a rich history that the world would be poorer for losing. And yes, if they stop having children or they lose their island then all of that will be lost.
Denying them this is tantamount to denying their humanity.