China has intentionally printed and destroyed currency to maneuver themselves against other countries. It’s one thing where you modify rates to influence inflation and spending but extreme manhandling your financial system means you are not a stable system to base the world economy on. While any country could screw everyone over, its the fact they have already manipulated things that makes them scary.
there is a difference from trying to stabilize an economy by controlling inflation and rates. We’ve seen China modifiy their currency maliciously. If China or Russia dont see favorable trade in their direction both would easily tank their economy to destroy other countries.