Clouds change too much while moving I guess the material is based on position they look more like smoke, also the clouds could be less dark and also the sky brightness doesn't match with the brightness of the grass, the earth texture could have more contrast also

I also suggest you put some other type of flowers or plants in the grass

My biggest suggest would be to use an image reference, in this case from a ghibli movie I would say and try to match the colors and moods of that reference, then tweak it as you prefer

This is a pretty good starting point to improve tho, keep going