What makes anti China propaganda so effective is that people want to believe it.
Believing that western system is fundamentally better allows justifying all the horrors we see day to day by saying that the alternatives are even worse, and so we shouldn't even try to change anything.
Accepting that China managed to find a better path that the west is actively fighting against means having to accept that the west is on the wrong side of history. That's a hard pill to swallow for a lot of people.
It’s often just white people being racist. They already had a negative opinion of them, so propaganda works well.
That’s a big part of it for sure, this is also what drives the whole Chinese people can’t innovate and steal everything from the west narrative.