Flatness
WordNet
noun
(1) Inactivity; showing an unusual lack of energy
"The general appearance of sluggishness alarmed his friends"
(2) The property of having little or no contrast; lacking highlights or gloss
(3) The property of having two dimensions
(4) A deficiency in flavor
"It needed lemon juice to sharpen the flatness of the dried lentils"
(5) A want of animation or brilliance
"The almost self-conscious flatness of Hemingway's style"