> What is taken quite seriously is the notion that China's first dynasty -- the Xia Dynasty -- never existed

There are some nuances about this. We know that there are multiple developed cities (and likely monarchies, given there are palace-like ruins) around or before Xia era. It's just that we don't know which one is so-called Xia Dynasty. But it doesn't meant that there were only small tribes and suddenly Shang came out of nowhere.