There are many good Chinese language films, not all of them Cantonese. You're forgetting about Taiwanese directors (Edward Yang, Tsai Ming-liang, Hou Hsiao-Hsien) and mainland sixth generation directors (Jia Zhangke, Lou Ye). There are also works by less known authors such as Bi Gan, Hu Bo, Xinyuan Zheng Lu - very unique and impressive.

One should not throw around ignorant blanket statements. There's a wealth of amazing Chinese language movie made outside of Hong-Kong, and yes, good artists can exist under authoritarian regimes, a prominent example of which would be Soviet cinema and literature.