To understand Tibet under Chinese rule, we first need to understand the history of Tibet. Far from a Buddhist paradise, before the 1960s it was one of the most brutal feudal societies on Earth. Since China’s occupation of Tibet, there have been measures taken to ensure the culture is restored while allowing Tibetans to better participate in wider Chinese society. In practice, this looks like bilingual education in schools to maintain the Tibetan language and the preservation of Tibetan temples.
To learn about Tibet before China, see Michael Parenti’s discussion of the issue here.
To be added: refuting specific claims of cultural genocide