Have you even ever been to China? The cities and outskirts are pretty clean. City Streets are swept everyday by an army of council workers and city streets washed and swept by mechanical sweepers. The big problem is the water and air pollution not filthy rubbish clogged rivers and river mouths. By the way I live in Sydney, one of the most beautiful harbour city in the world but if you look hard enough you will find rubbish in the water
I have. In 2015. Cleanliness is relative.
Have you looked into the Huangpu river right under the iconic pudong skyline that looks so pristine in glossy posters? You are unlikely to find rivers that streaming with discarded flotsam in most of the developed world.
Also, the streets in Shanghai may be washed and swept once a day, but the amount of debris and detritus customarily tossed offhandedly by the residents are such that the streets are nonetheless more littered by far than is commonly encountered in most developed cities.