The issue is that the outskirts seem too green and brown.
I’ve went on google to look at references but to no avail. All the images were not what I was looking for.
There are many elements to making the tropical look more realistic or vibrant:
-Rocks
-Fallen logs
-Mud between sand and grass
-Lighting changes
-Different types of trees and foliage
Its probably best to watch a YT tutorial on this, since it requires many things to be done, and they will show you what to do.
the turf is very planar for being an island. Islands form when tectonic plates fight each other, the ground should be all wobbly, uphill and varied when it gets grassy. Right now it looks like a light storm would flood the whole island
The trees aren’t varied enough, natural trees grow in many different sizes. I’d also add other plants, it’s weird to see only trees and grass.
Also, pine trees next to palm trees doesn’t make sense. They’re from different environments.
The terrain is way too flat. Islands usually have lots of elevation variation. Also, the terrain isn’t varied enough. Try mixing in the Ground and Mud materials to make it feel more natural.