Your biggest problem is the choice of art style. You need to go for a style that fits the tech.
There are different voxel technologies, each with its own pros and cons, and if for whatever reason this kind of grass is a must, you should look into voxel techniques not based on poly meshes, but on a pixel conversion from a 2d heightmap, as was done in earlier eras.
But given what you are working with, and that I personally think this kind of random noise grass aesthetic is not a desirable look to begin with, you should go for a more comic style. It's all about conserving your details for where it matters most visually. It can look surprisingly rich if done by a good artist.