flatness

the property of having two dimensions

a want of animation or brilliance; "the almost self-conscious flatness of Hemingway's style"

a deficiency in flavor; "it needed lemon juice to sharpen the flatness of the dried lentils"

the property of having little or no contrast; lacking highlights or gloss

inactivity; showing an unusual lack of energy; "the general appearance of sluggishness alarmed his friends"