Why do my low poly walls look this way

I've created some geometry using `Mesh` and have put it in my scene. But despite making sure every face has it's own set of vertices and that all the normals are facing outwards, I still have a sort of blobby look around the edges.

https://sli.mg/6fHCk3

You can see it on the dark edges on the side of this ridge. What causes that? My texture doesn't have that, the texture is very very plain. Those are supposed to be perfectly flat and low poly, but it looks like there's almost a shadow creeping around the corners of it.

I'm using the default (untouched) light source. Material is also all defaults.

Code (csharp):

1.  
2.         Mesh mesh = new Mesh ();
3.  
4.         mesh.vertices = vertices.ToArray ();
5.         mesh.triangles = triangles.ToArray ();
6.         mesh.uv = uv.ToArray ();
7.  
8.         mesh.RecalculateBounds();
9.         mesh.RecalculateNormals();
10.  
11.         return mesh;
12.  

 

Try switching the anti-aliasing quality into x4 or x8 multi-sampling in quality settings.
Or add an anti-aliasing image effect may solve the issue.

 

To fix:

Set the light source to either no shadows or hard shadows, or on the mesh renderer turn off receive shadows. Thanks guys for helping me.