Just thought of something else. If you have problems with virtual textures looking blurry in general, you can try increasing the tile size in your project settings under Engine/Rendering → Virtual Textures → Tile size. Normally, this wouldn’t matter, but it does start to matter on large areas such as landscapes.
I found that enabling Anisotropic filtering is also very good. Requires a bit more memory for textures, but what this does is help with textures seen at an angle. Walls would be the exact opposite since it is flat on the view. But landscapes are very prone to being viewed at an angle.
If you’re not using RVT, I think you need to set “Draw in Main Pass” to “From Virtual Texture”. Make sure you have no RVT volume in the scene. I’m not sure on this one, but thought I’d mention it.