The poem starts with something ordinary: buying fish. But the fish come from "a wretched dirty sea," and that small detail casts a shadow over the whole shopping trip. The speaker and those around them bought four, and the poem quickly turns the purchase into a confession. "Easily persuaded almost to anything" sounds like a self-portrait of people who go along with whatever is pleasant or convenient.
The third stanza sharpens this. Offer us love, the speaker says, but never science. That suggests a preference for comforting feelings over hard facts, perhaps the kind of facts that would tell us how dirty the sea really is. The title, "Out of sight, out of mind," fits: we don't look closely at what we'd rather not know.
The last line is the most uneasy. The speaker asks to be made thankful for being at ease, even while wronging the poor. The mood is quietly guilty and ironic, as if the speaker sees their own comfort and can't quite stop enjoying it.