Sure. When I say postmodern, I am referring to primarily postmodernism in sociology. Postmodernism at a high level typically refers to skepticism of that which is defined as the norm, reality, or concepts of modernism (religious values, industrialization, urbanization to name a few). I'll share the link to the following definitions that define postmodernism in the sense of sociology.

"Postmodernism in sociology is an analysis of the social and cultural features of late capitalism (post-modernity), a critique of sociological theory as a modernist project, and an extension of sociological inquiry into new domains."

"The key concepts of sociological postmodernism are subject, identity, text, and symbol. On these grounds, postmodernity is characterized as a form of social order in which the electronic media play a prominent role, symbolic codes are pervasive, and social identities are fragmented."

https://www.sciencedirect.com/topics/psychology/postmodernism

I say dystopian because typically in films and novels, a depicted utopia is actually a dystopia. The convenience that this offers sounds nice in theory (especially when instagram markets itself as a platform for self expression/art and discovering and portraying one's identify) but to your point, it's just consumeristic and doesn't highlight the exploitation behind a lot of fast fashion brands and their unsustainable business practices. I agree, this is a very modern happening. My comment is meant to highlight how unreal it all sounds.