That’s just happening because it’s using mipmaps for the furthest away triangles in the scene. You could make it look better by adjusting a few things:
Use trilinear filtering (to blend between mipmap levels). You’ll still have the blurry effect but it’ll blend together better.
Use anisotropic filtering (the camera is at an oblique angle so this would improve the look of the textures in this case)
Change the texture mipmap bias so it’ll use the larger resolution textures for higher z values.