You're right that the particular quoted statement has a Marxist/Leninist flavor. I'm not sure why that writer (who, as far as I can tell, is not connected to the documentary except in that the filmmakers thought his article was relevant) included that statement in his piece, which is a fairly good explanation of the process of gentrification.

But, to respond: Classes in American society clearly are not going to disappear anytime soon, for better or for worse. Gentrification is the process by which working-class people find that they can no longer live where they once did, and that is a process that we hope to be able to do something about.