It's amazing how respondents ask 'have you done AF Micro Adjustment (AFMA)' again and again and there is no confirmation from those with soft images. I remember a big rant ages ago from people saying the same with the 7D II and most had *not* done AFMA.
Very small amounts of AFMA (+ or -) can make an epic difference to pixel level sharpness. If you are, say, 6 points out on a 24mm lens, your focus point will be a country mile out. You will definitely see 2 points as a clear change in 'bite' at 24mm.
AFMA is required on every single lens you own on every body you own. Many will require zero alteration, but some will require quite a lot. Now, there may of course be some issues with 'bad' 5D IV bodies out there, but with nobody confirming or denying that they have done AFMA, or at least used live view focus (which takes focus directly off the sensor of course), one can only suspect AFMA as the culprit in most cases.
My first 24-70 f2.8 L II had a heavily damaged package as if the courier people had dropped it out of a plane. The result was left side softness with the image and focus problems using any left side AF points (presumably because the image did not generate the contrast for effective AF). On centre it was bitingly sharp wide open with zero AFMA. Out of the box, the replacement lens was fair, but clearly lacked the same bite on centre. Two points of AFMA and it was in razor blade territory at 24mm.
I think Dustin Abbott's example shows precisely what the sensor is capable of and its clearly a very significant advantage in resolution over the 6D.
FWIW, I also own both A7 and A7R. With the best lenses, at the best apertures the A7R has fractionally better pixel level sharpness (as well as having more of them), but you really do have to be at the right apertures on top lenses to see this. Most of the time, once carefully sharpened, the A7 images look roughly the same as the A7R files at the pixel level, despite the presence of a (not mild) AA filter. Unless Canon has gone mad with the AA filter (why would they, especially as the higher MP count will allow the filter to be less aggressive than on the 5d III), the only likely explanations are:
1. AFMA
2. Software
3. 'bad' bodies floating about.