I have the same problem, but inconsistently. Sometimes the preview is fuzzy or pixelated, other times it is normal. Very annoying!
Could you please let us know which operating system are you working on?
Also, could you try resetting the preferences of Photoshop & let us know if it helps?Preferences in Photoshop
I reset preferences, and it appears to have solved the problem. I won't know for sure for a while, as the problem was not always present. Thank you for your response. I am running under Windows 10.
Edit: Did not stay fixed - print preview is again blurry.
I'm running Mac 10.12.6 (Sierra). I just reset the preferences, but it's still happening. I'm also noticing that when I reduce the size of an open window/image, the image reduces in size, but the window frame stays the same and doesn't reduce with the image. I have to then hit command - or command 0 to get the window to be the same size as the image. Enlarging the window size/frame works normally.
I have the same Problem with Windows 10 / ATI FirePro V4800 (FireGL V). Adobe support recommended an driver update for the graphic card to the newest version. But it has no effect, preferences reset has the same result.
In addition I installed cc 2017. This works fine, but this isn't the solution I want.
Version 19.1.0 works fine on my laptop (ASUS Zenbook, Windows 10).
Unfortunately no solution by version 19.1.1.
Additional observation on this issue: When the print dialog opens the preview image is less sharp that in previous versions, but selecting a different printer profile causes the image quality to degrade. Reselecting the original profile does NOT restore the image preview quality. I am running v.19.1.1 on Windows 10.