World trade wasn't really dynamic, it was pretty much pre-destined to pass through to the highest population centres because of the demand.
Using this as an concept for trade, everything ends in China. It was simply the largest and most prosperous region during the games timeframe. The real reason why Britain begun the Opium Wars was due to China swallowing such gigantic amounts of silver, the entire world trade was concentrated on silver flowing towards China.
In Eu4 you simply pull, you don't pay for it. You can pull as much as you want, but there is no bill. Trade is a transaction, a bargain between two parties who barter with one another. Eu4 trade is about pulling stuff towards your home, not real trade as we know it in real life.
The money that England, Netherlands and Portugal made from global trade was spent on buying goods from China, moving the goods towards Europe, making profit with that, and then buying more goods from China with the profits. Europe got the goods, China the money. Porcelain, tea, silk... in exchange for silver. Until the majority of worlds silver reserves were circulating in China and Britain realized "oh snap" and one thing led to another... Opium Wars, burning of Summer Palace, Taiping Rebellion, carving China like a cake, Boxer rebellion, Chinese revolution... All so that Europe could get their precious silver back.
To make the trade more real, a country that pulls trade would have to pay for the local goods it decides to move elsewhere. For a more realistic gameplay, we would have Europeans pulling chinaware and silk from China to Europe around Africa, and meanwhile moving furs from Siberia to China and furs from Americas to China, silver from Peru to China, gold from Mexico to China...
Even the "Triangle trade" fails in the game, simply because Africans do not actually benefit from Europeans moving weapons, cloth, metals, food from Europe to Africa. Instead now Europe collects stuff from Africa, sends stuff from Africa to Europe directly and indirectly via Caribbean.
China was the heart that kept the global trade flow beating for many centuries until late 19th century, and now it looks like it shall reclaim its place somewhere in the middle of the 21st century.