White highlights make the map look "glossy", the lighting would look more "diffuse" if you made the background colours lighter or darker rather than just adding white. The forests have a similar problem, it makes them look like they were made by dripping green wax on the map.

Also it's really dark overall, which makes for poor contrast and poor readability.

I'd recommend trying to think about two things while map making:

What information am I trying to convey and how can I convey that as effectively as possible?

How would the in character cartographer I'm mimicking have done this, and how can I best replicate that?