FYI this is called Ambient Occlusion, it is used to add realism to a game because without it everything looks flat and nothing that is not a light can be that bright without any shadows in real life.
I do not think ROBLOX has added a feature like this, it’s not a situation where you need to change the lighting, I recommend for now until ROBLOX add a shadow removal feature, I would use FYI , which @vsnry had mentioned in his comment. However, another way would to add spotlight or pointlight to an invisible object.
I know this thread is a bit old, but I found a solution. With the new ForceField material, if you apply it to a mesh, there is no fancy lighting to it, and if you turn off the CastShadow property, then the part should be perfect your what you’re looking for.
It’s called SSAO or Screen Space Ambient Occlusion. In real life light is ray traced and in corners there isnt a lot of light to reach so it gets dark (the shadows u see), but because roblox doesnt use ray tracing it uses SSAO and its there to add realism. If you want to remove it you can add a Bloom object in the Lighting and set the Intensity to 0 and then make the parts from neon. They won’t get any shading (even diffuse lighting) but thats the only way. Roblox is now going for realism so you can’t technically stop it. Also SSAO adds more depth witch makes it easier to distinguish objects one from another. Removing it will just make the objects undistinguishable.