That said, I’m not sure I agree with your assessment that it’s wrong, exactly. Postmodernism did indeed follow modernism and come into being as a reaction to modernism. So I think “postmodernism” has a naive and original sense of being “what follows modernism”. Decades (so many at this point!) of discourse have added layers to that and undermined it and generally made it more complex. But the underlying meaning of the term remains.
(If your instinct is to respond with arguments about how works not limited to late 20th century western culture can be nonetheless classified as postmodern, I hear you, but the fact that the term itself was only coined post modernism remains, and is all I’m pointing to.)
Personally, I get more hung up on people using “modern” to mean “new”. Then to use “postmodern” to mean “more new” while to my ears (eyes) it means “dated af” is even funnier and more jarring.
Helix, the first editor to not believe in grand narratives. Helix, the relativist editor. Helix, now updated with the latest from Foucault and Derrida!