Just as “Unlit” sounds, it means that there are no light in the scene, meaning that everything will look flat/dull and details will have minimal visibility. When you have a “default” material in Blender, there is still light emitting from somewhere to show the details. I am thinking of those 3D softwares as a photo box (where light comes from all walls + ceiling and floor).
Maybe create some sort of light box where you place the meshes inside with a grey-ish material or something.