Regarding the 5700XT I can't say, but I can tell you that everyone that I recommended the nvidia buy (specially in the bitcoin era), most people from family, friends and known, almost all them told me they noted image quality degradation going from radeon over to geforce.
And if it was an upgrade where the new card was faster than the previous one is even more strange to me. Desktop, videos or gaming all complained, strangely it's something that can't be shown.
I could not compare since I was not the regular computer user so I could not clearly see what they where actuality saying and showing nor I could remember how it was before.
But when it was a radeon to radeon upgrade I never had anyone bothering me with image quality problems.
Since I was in some of the peoples homes adjusting monitor gamma and contrast/brightness settings and didn't solve/fix, at best improved a little, I searched a lot the net and many reporting exactly the same, so it's common.
The more common fix that you can find on the net is this one in the amd forums and didn't work:
Why does Amd give out better colors than nvidia?
(post from apriores and ajc9988)
From nvidia their own tips also didn't work/fix:
GeForce Garage: How To Calibrate Your Monitor
If someone else is saying the same else where, maybe there is really something going on,
here enjoy 31 pages on the subject 
Nvidia forums are also full of
the same complains