Abstract (meaning non-representational of objective reality) art can be appreciated for color, form, and composition. It can also be admired, as MikeG has expressed, for the degree of craftsmanship, ie work, put into the creation of the piece. It also might evoke emotions unbidden if you gaze at it while allowing your critical, intellectual faculties to recede.
You're under no obligation to appreciate the work on these or any other bases. But please don't let that lead to the conclusion that those who do appreciate it are somehow insane, or stupid, or wrong. Aesthetics are subjective.