That isn't the reality I see on the ground. Take a look at for example this Tibet documentary:
https://youtu.be/zkYhSsQqRhI
This Tibetan woman has 3 husbands. Look inside her house: full of Tibetan and religious artifacts. And this is just a normal Tibetan household, after we've been told for decades that Tibetans are being culturally genocided.
It looks to me that Tibetan scripts and languages, Mongolian scripts and languages, etc are better preserved than over the border in India and Mongolia.
Yes there are also plenty of examples where they tear down a cultural site. Yet I think there is a fundamental difference between western and Chinese interpretations of such acts. Western societies have developed a sort of mythical worshipping of traditional ethnic culture. To the Chinese, to whom development and modernization have come late, development and modernization is number 1: there is no pride in living a traditional, ethnic life if that means being in the middle of poverty. Some sites are torn in the name of development. See this discussion from 1999, back when the China topic wasn't so politicized: https://www.theatlantic.com/magazine/archive/1999/02/tibet-t...