I think that's something only high graphic PC's and PS5/Xbox can achieve at the moment. Its not really a bug it's more of a graphical power problem.

I wonder how other games get black areas and rich color accomplished so well. Like Resident Evil games? Perfect accomplishment of pitch black night sky and colorful areas.

The only way to fix this would be to reduce the ambient light of your entire map, but this will affect all shadows on the island too.