What strikes me is that MH Wilds looks like a very polished PS4 game in most instances running at 4k.

Nah.  Way more on the screen.  Way better particles, volumetric and lighting.  MH Wilds looks stunning.  

Japanese developers and PC optimization...now that will be the day.

At least Kojima Productions did a good job with Death Stranding!

Yeah, there are always exceptions of course, and it did get better than it was - not that western developers are really that much better, but still.

GPU/RAM wise it was excellent by 2013 standards, yeah.

It's weakest link, like all 8th gen home consoles, was it's CPU, which was slow even by the standards of the time. The fact that it still manages to run a current gen game like Jedi Survivor is something of a minor miracle in that respect, as CPUs in PS5/Xbox Series run circles around the Jaguar cores in PS4/XBO, and CPU demands can't be scaled as easily as graphics.