The speaker of "unique" imagines their own death or absence and decides it wouldn't matter much. Nobody would care, they say, and then the sharpest admission arrives: "not even i do." The usual comfort that we're each one of a kind gets turned upside down. Being "unique" here doesn't feel like a gift. The speaker suggests that even their loss would be ordinary, one more disappearance among many.
The feeling is flat, tired, and numb rather than loudly despairing. Short lines and no punctuation make the thoughts sound quiet and matter-of-fact, as if the speaker has gone over this many times. "I'm everything that isn't" is a puzzling, slippery line. It suggests someone defined only by what they are not, a blank rather than a person. The ending, "just here / and there," is pushed far across the page, which makes the speaker look scattered and barely anchored anywhere. The mood is lonely and hollow, and it asks the reader to notice how heavy it is to feel unnoticed, including by yourself.