China is inexperienced in modern diplomacy. But it is a fast learner. I bet we will see a different China in 2030.
I wouldn't agree with such a characterization entirely. To understand, think about this way:
Firstly, think about where PRC has come along from between '50s-'70s when its was so isolated in the world stage. How it had maneuvered against the two superpowers of the time which were both hostile to it. It regained its permanent member seat of the UNSC in the '70s and reintegrated into the global system without giving up its autonomy, and has become what it is today. Diplomacy has played a large part in it.
Secondly, don't just look at western countries. China has friendly relationships with most of the countries in the world. This is evidenced by the facts that in UN, where China has gotten supports in major issues, including Hong Kong and Xinjiang. Also look at China's strategic initiatives, such as Belt and Road Initiative - its summit was attended easily by most state and government heads outside UN assembly, in the words of the well-known US political scientist Ian Bremmer - and AIIB. Again, diplomacy has played a role.
Thirdly, look at what China is against now. A few hundreds years of western dominance and their vast media and influence and intelligence networks. The west feel increasingly threatened by the rise of China and have felt the need to collaborate in many fronts to make China a "bad guy" in the world (in the words of a CNN correspondent recently). It's amazing that the NGO-media-policy industrial complex can make a non-issue into a genocide involving one million err I'm sorry three millions Uighurs going through reeducation camp aka internment aka concentration camp plus forced labor plus sexual slaves. They have been quite successful judging from how brainwashed the western population and politicians on this. What kind of diplomacy would China have to deploy against such an odd? I would say they're doing not too bad giving the odds.
There is no doubt Chinese diplomacy needs improvement; we can always find incidents where they can play better diplomacy - I personally do. Especially now when China's adversaries are doing their best to disrupt and discredit China ("extreme competition"), China needs to bring their A-game to diplomacy. I hope they learn and improve, better quickly.
I would give you, though, that modern diplomacy is more a western game.