The title, "Plus ça change," borrows the old French saying that the more things change, the more they stay the same, and the poem is a bleak joke built on that idea. The speaker describes the frustration of hoping for social change as something like a stillborn child kept "fresh in salt": a hope that never lived, yet is preserved and handled as if it still mattered. The image is startling and a little grotesque, and it sets an uncomfortable tone right away.
In the second stanza, "we" press the "little ex-hand," a phrase that is tender and morbid at once. Then the poem swerves into the ordinary: after some time at the office, we "die of apoplexy." The drop from the dead child to a desk job is the sharp part. The poem suggests that our anger at a world that won't change gets absorbed into routine, and that routine finally kills us. The mood is bitter, darkly comic, and resigned.