And your initial response, that it's the future, should suggest to you why they've chosen it. They want us to feel doomed to repression, presumably under their ægis.
The idea is to get with their program and pass on the desire for better (more modern) times and revert to the more primitive, pristine state.
Sure, where life was "nasty, brutish, and short."
See? It's like everything else that the Progs are behind, it carries with it a need to double-think what they are really up to. With their coining of post-modern they have begun to take us back. Like toilets that don't work well. Like insisting we leave kindling on forest and meadow floors awaiting the next spontaneous combustion (let alone a lure to arsonists and terrorists) to destroy homes in addition to wildlife.
I'm not suggesting you accept their term, but understand why it exists. And indeed you should hate it.
For myself, because of their ongoing assault on our comforts, I use the term contemporary times instead. I wish to reserve the term modern for a future that is more modern and not get-over-the-pursuit-of-the-modern as they wish.