My wife and other Chinese people will tell me to avoid some local restaurants and just cook at home because of poor restaurant kitchen habits.
Produce in big supermarkets aren't always so fresh. They keep them on the shelves until they rot.
I'm often told to buy produce from local market places where the farmers and vendors bring them directly from the farm which they grow crops.
The main complaint I hear some people say about Chinese food quality is that it's too oily or food is prepared with gutter oil, however I only think that some foods are made too oily but not most of Chinese Cuisine.
I'd say that a lot of food you buy in restaurants in China are quite oily. I'm not sure if your location is different, but here I would agree with other people that a lot of it is oily. They cook a lot of stir frys so you can expect a lot of oil.
That's all around China. I haven't seen much of difference in each province, besides small shops vs upscale restaurants.
The stir-fry dishes are oily. Some baozi are oily. Some small shops have served me some very oily fried rice. The continuous use of the same oil is the food concern with expats here. The street food some people don't trust or deem it has poor quality.
Sometimes one incident leads to the general belief like that baby formula incident years ago. They still use that as the excuse to buy imported baby formula over domestic.