The current Level.png for the Tutorial map is old, low-res (1280x720), and just generally poor in quality.
I suggest updating it to match the standards of the “normal” playable maps (which are 3840x2160 pixels in size).
Additionally, the “Destruction” demo map doesn’t have a Level.png at all, and should be given one for its use on the map select screen and the loading screen.
Addendum: