This is similar to the common sentiment people have about advertising: It's so stupid... never works on anyone I know. I don't know why companies waste their money.
Meanwhile, advertising is an industry that rivals energy, shipping and such. If that's not markt proof of efficacy, IDK what is. From the advertiser side of the advertiser-consumer relationship, there's no doubt of efficacy. You open an online business. No one shows up. You advertise. People show up. Profitable or not, the causality is plain.
Consumers only notice that ads piss them off. Advertisers only notice that ads make consumers do stuff, and both think the other is dumb.
Believing that Chinese propaganda is ineffective is naive. It's a carrot and stick system locally. Internationally it's just carrot, but carrot removal is a lot like the stick.
When Deng he decided to liberalize the Chinese market, he had some saying about the danger of letting flies in when you open a window for fresh air. Fresh air meant the economics. Flies meant cultural-political influences. Mcdonalds, yes. Youtube, no.
Now the tables are turned. US media, entertainment and sports companies want into China for its market size and growth potential. They enter on China's terms, and those terms are always unstated. Increasingly, they relate to stuff entirely outside China. Favoured companies will succeed, misbehavors will not and we will rarely be able to say exactly where "propaganda" is at play.