Communists had great propaganda during the Cold War. So good that liberals still get upset when you simply show them their own problems when they want to waste resources "combating injustice" elsewhere. If you're referring to modern day leftists, then it's because no one even wants to hear the word "capitalism" because their knee jerk reaction is to rabidly defend it and bring up the sins of communism even if all you're doing is literally repeating what capitalist scholars, journalists, and economists have written.

Imagine Barbie but with class-consciousness. With all the basically free high-production tools and talent on the left, is it not possible?

You must not be familiar with Bong Joon ho, squibgam, Oliver Stone, or Costa Gavras. However, even when you're staunchly leftist, most of the game you'll have to reach out to a big distributor to show your movie. If it's not a genuine threat to capital, they'll happily show it to everyone. "The film performs our anti-capitalism for us, allowing us to continue to consume with impunity.