I fully agree that Shanghai is becoming much more dynamic than HK. In a few decades, I expect it will all but kill HK (particularly once direct trading starts between the Mainland and Taiwan). But your history is a bit off. Shanghai was a small inconsequential fishing village (not unlike HK) until foreign traders built it into a financial center in the 19th century (not unlike HK). The only real difference between HK and SH historically is that HK was a British Colony until 1997 while Shanghai has changed control a number of times (Colonialist, ROC, Japanese, PRC) and suffered greatly as a result. Today Shanghai is a much more exciting city than HK, but it's still far more similar to HK than the other 99% of China. Cities like Xi'an, Guilin and Lijiang offer a much greater contrast to HK than Shanghai does (albeit a somewhat disneyfied experience). I'm not saying people shouldn't visit Shanghai. It's a great city with plenty to do, good people, good food, great lodging, good shopping, and the excitement and ambition of the city is absolutely pervasive. But its history is not ancient and if the OP is sick of HK, I think there are other places to go to get something different. Xi'an if you want ancient. Guilin if you want scenery. Lijiang if you want Disney-quaint. Beijing if you want displays of power.

I also really enjoyed my travels near Lijiang, but I think you have to change planes in Kunming to get there from HKG/SZX/ZUH/CAN, so that may rule it out for the OP.