if you want to desaturate the whole scene you could try just modifying the default post process (in worldinfo). There should be a setting in there which will desaturate the scene.
It's probably that and the complete lack of shadows. Not to mention I used default scanline for that while using Vray for the high poly. And here are the wires for that Notre Dame piece:
I've opened up the max file that comes with the tut. Is there a reason why the Gamma & LUT settings are enabled and set up to 2.2 instead of the default 1.0?
Update: worked on the lighting and finished adding textures and some more geometry to create the bricks in the crack. Brick texture is the one from the Unreal4 Default Materials.
Im fairly sure I had this similar problem. For me it turned out to be the Wacoms driver needed to be cleared and restored to default settings. Hope this helps.