I agree with the observation that Planescape's setting belongs to the Reason Era. But no gunpowder please
I feel that the whole idea behind it was to present the Planes as something more grandeur, deeper, and transcendental in contrast to your regular Prime Material World. You could present a Prime World in the same way, but it wouldn't feel exactly right as far as DnD Cosmology is concerned.
In our current campaign, we traveled from the Planes to the Prime Material World. While we were constantly challenged (mostly mentally) on the Planes, on the Prime it feels like we're on a vacation.