Just image if it was a 3d model. You could optimize it, create a new high poly for it, bake it down, create new UVs and textures, and LODs, but it’s still not your own original model and you cannot resell it. Even though there’s nothing from the original model that was untouched.
You could though, deconstruct the project, figure out how it was made and put together, and make your own version of the same blueprint (hopefully making a better version with more features). And you could copy and paste chunks that you made from fixing that project into a new one.