Another technically impressive Witcher 3 feat was the Switch port, it ran really well. Goes to show how much can be done with optimization and how much resources are wasted on the PC purely by bad optimization.
And with using much lower quality textures and 3D models, therefore using much less RAM for assets. It's not an apples to apples comparison and you can't really make claims about bad optimization on PCs when the scope of what's shown on screen is vastly different.
You too can run Witcher 3 equally on a minimal PC if you're willing to set the render resolution to 720p (540p undocked), settings to below minimum, and call ~30 FPS well.