The notion of overpopulation relies on a logic of Malthusianism, which is eugenecist. Allusion only requires an indirect reference. So by referring to overpopulation but not to eugenics, the effect is an allusion (indirect reference) to eugenics. I accept that you may not have intended this.

This allusion would be strengthened were you to suggest, though, in the context of saying there are too many Chinese people, that China should depopulate itself for the good of the planet, without addressing the unsustainability of capitalism or of the lifestyles (not lives) of those who live in the imperial core.

Even though there are roughly the same number of people living in the global north as in China, the habits of the inhabitants of the global north, due to their capitalist political economy, are overwhelmingly driving climate change and destroying biodiversity.

It's hardly playing the victim to point out that eugenicist arguments are bad, nor that westerners should have to change their models of consumption and production to ones that are far more sustainable long before we get to the question of who should not have children. And when we do get to that question, the answer should be anything but based on race or ethnicity because that would be abhorrent.

How else would a state curb the excesses of capitalist logic except by consciously being authoritarian? This very power, exercised by the working class, is why China will achieve so much.