They don’t want immigrants who won’t assimilate and who don’t bring any real value,
I think they were being polite.
Japan wants almost ZERO immigrants, whether they bring value or not.
The Asian nations are VERY much aware of their race and their racial heritage and culture.
From Wikipedia:
Ethnic Japanese make up 98.5% of the total population
About 1.6% of Japan's total legal resident population are foreign citizens.
Asian countries have absolutely no problem with their "racism", Japanese citizens living in Japan don't live in fear of being called RACIST!, and they have no problem with their immigrants, because there are virtually none.
America used to be like that.
Not really, it was the opposite. Nearly everyone was an immigrant, or descended from one or more, so it was not an issue.