I think the fact that there's a well-lit column on the outside of the building right where it cuts off is what makes the cutaway not read like a cutaway. None of those columns should be so well-lit.
Grass IRL is noisy, but this is where stylization comes in - humans rarely think of (consciously perceive) objects the way they are, and simplified grass will often read more like [grass] than something that reflects attributes of grass that people don't tend to think about, like the fact that it's noisy.
Overall, I think a clear, effective image is more important than realism, especially in pixel art. In addition, having "realistic" grass in the same image as the highly stylised, simplified trees and ruins just looks odd. I think cleaning up the grass would be best. You can still make it look long and textured without making it noisy.
