I thought this was removed from the game, or just this was the way to “improve” it from the original game, but I see that this type of illumination was only removed from certain maps.
Age of Empires III DE | Original VS Remaster | Graphics Comparison | Final Version - YouTube
I also thought that the water perse was the one that had this type of illumination tone, but in the editor I realized that this goes in the type of illumination.
Personally, that tone of the sun that begins to hide in times of autumn seems better to me. (Or what exactly does it represent?)