This was almost the absolute tail end of separate systems of international diplomacy and law. The British were working under the Westphalian system where there’s a pretense at legal though not practical equality. Under the Confucian system China was the hegemon and all others were subordinate. States either paid tribute and were civilised tributary states or were barbarians. See how the Macartnety Mission refused to pay obeisance and thus was refused leave to establish diplomatic relations in 1792.

https://blog.gale.com/the-george-macartney-mission-to-china-...