Minecraft textures blurry and low quality:
Open Minecraft
Enter Game
Toggle Fullscreen (F11)
Minecraft textures clear and high quality:Open Minecraft
Toggle Native Fullscreen (Green Button, left corner)
Enter Game
With a good eye you can easily spot the difference, on a 5k Screen they are very noticeable.
Linked issues
duplicates 1
Comments 1

Thank you for your report.
However, your ticket has been resolved as a duplicate.
This issue has been linked to the original bugreport: MC-76652. You can find or add further information on that report.
Please search before reporting any bugs, as it's likely that one exists already.