China is de-oiling at a rapid pace and wants to lead the world in renewables infrastructure production. Which will mean eventually butting heads with the oil producers (which also includes the US). China is also getting cheap Russian oil, and the Gulf states have proven to be unreliable allies for them.
China doesn't produce plastic as is. They produce plastic products, after buying the plastic from oil producers. The largest plastic raw materials producer is SABIC, a Saudi company.
There are currently no viable alternatives for humanity to replace plastics in daily use while still maintaining the low cost of those products. Unless humanity opts for more expensive material to subvert plastic consumption, plastic is going to be used regardless.
And China is simply feeding that demand in Western countries with those goods, because those countries want those goods for cheap.
