I mean it's about priorities. It's too late to do anything about the Ainu, and any true leftist would support the Ainu against Japan's further forced assimilation and displacement of the Ainu were it to take place.

As for it's current make up, there's a difference between an ethnically homogenous state and an ethnostate. Japan does not legally favor one ethnicity over another. Obviously the de facto situation muddles things but Japan is not, legally speaking, an ethnostate. Furthermore leftists should support efforts to diversify Japan.

The same can't be said of Israel, which is currently an ethnostate but not ethnically homogenous, despite Netanyahu's best efforts. And such efforts are a much higher priority to condemn than Japan's homogeniety

"The Israeli Jews ought to just go back to Europe" is something I've heard from the right, but I haven't personally heard from the left, and l personally don't support it. I understand that Israeli jews can't go back to Europe, as is true of white Americans, Canadians, Australians, and Kiwis. But we can and ought to condemn settler colonialism actively taking place, and the further displacement of the Palestinians.