I love symmetry, harmony, and repetition a lot: as compositional elements they make my brain very happy. During the editing process I’m not above removing small incongruous elements, if I think they detract from the overall scene. Painters leave things out all the time; photography doesn’t need to be any different.
That said, incongruous is not a value judgement. The strange, unusual, or unexpected can enhance a scene. It can be the scene.
It’s all a matter of perspective.