There's plenty of evidence of China trying to improve the living conditions for Uyghurs in Xinjiang and in the rest of China (poverty alleviation, affirmative action programs for university students, the crackdown against hate speech on social media, ...). So imprisoning some people based on some vague "extremism score" and then seemingly releasing them after some months doesn't show intent to impose living conditions in order to destroy a group. It shows intent on crushing separatism.

Preventing births is true for everybody in China, how does that show an intent to destroy a particular group? It doesn't.

So we're left with "serious bodily or mental harm", which can be explained just as well by an intent to suppress separatism and religious extremism. Literally every war causes some nationality "serious bodily or mental harm" far worse than what China is doing, and we don't call every war a genocide, do we?