I'm also very interested in this topic, since I'm in the process of adding in Outerra-like procedural planets to my space shooter.

I believe that your problem is that your terrain texturing is all one frequency. Since all of your terrain texture is a high-frequency sand-like texture (which looks good up close), when you go to a distance it all appears to be smooth due to mipmapping (and if you didn't use mipmapping you'd have aliasing artifacts).

Using fractal noise to calculate your surface will produce more variable surface normals and take over for the detail when the surface detail texture frequency is undersampled. But I'm no expert, perhaps there's something more that can be done with a purely texture-based approach without getting into fractal noise.

You are focusing on texturing but forgetting shape itself. Your terrain looks fake because of lack of details on the ground, like cavities and errosion.