This might be true for absolute beginners, but even without any shder writing I am able to select a material without spec and without normal mapping as an example to render faster.

I would agree with you when it comes to mobile devices. But the engines I know also come with many dedicated shaders for each mobile platform. So it is already possible to select only the desired effect and not a master overkill shader.

As an example there is a normal mapping shader for iOS that has a fixed constant lighting position (one light only) to speed rendering up.

Besides that I am not sure what kind of "artists" you know of. But the ones I am in contact with all have a programming background and know for sure about performance issues.