It is surely good for 3d printing but yes for sure it is not good as a material. There are some tweaks to output mesh vertex color to an image in order to use this image as a texture for a material. So it could be used then in a renderer.
I also had to make my own workflow in order to do that for texturing objects (mesh or breps …). You could reuse my code with your shader (transformation XYZ to a color). You just need to put some UV on you mesh.