A disappointing review.
Indeed, it's a poor review.
You can sometimes get better results from the raw files (ISO 3200).
Need I say more after such a comment.
Okay, ISO 3200, on a studio camera, get real. We already knew this wasn't a camera for underexposed low noise results, it requires proper exposure and controlled lighting (or bracketing) to make stunning images.
Judging based on OOC JPEG's, get real. Ever heard of good Raw conversions, deconvolution capture sharpening?
Maybe the AA filter is too strong, the lenses not good enough?
Nikon have had more time to get their lenses in shape for hi rez.
The 5DS R has a low-pass canceling filter, and the redesigned for digital lenses of recent years are quite good, even the zooms. What apertures were they using? Looking at Diffraction at the pixel level? I'd suspect the tester's Capture sharpening skills are also poor or non-existing.
Try a Raw conversion (even with a mediocre converter like ACR) of one of the base ISO shots at Imaging Resource, and use proper Capture sharpening. Resolution is excellent, as expected, color looks nice but we need to wait for e.g. Capture One's take on Raw conversions and ICC profiling to compare with ACR.
Cheers,
Bart