It's post-apocalyptic in the sense that it's set (thousands of years) after "the Breaking of the World" - a disaster which happened as a result of Male Aes Sedai (primarily The Dragon) going mad. The "Breaking of the World" was a truly cataclysmic event, with mountains forming where seas once stood, old mountain ranges torn down, the whole world rearranged and made anew.There's no hint of modern technology from a post-apocalyptic Earth that has been lost - such as radiation, mobile phones or vehicles.
It looks like medieval Europe - with the landscapes, the technology, the customs. Such as horseback riding, drinking and singing in taverns, sword fights.
Post-apocalyptic doesn't mean that it's post-modern, just that it's set after an apocalyptic event.
For what it's worth, the books do mention some technologies which were lost as a result of the breaking - glow globes and stasis boxes are two which spring to mind. But that's not to say that these correspond to anything in the modern world as we know it.