The poem looks at the industrial revolution from the point of view of people the mills left behind. Its opening claim is blunt: the mills made some people "unnecessary," while others grew along with their fortunes. The speaker sets "us" against those winners. "Us" are the ones who "use hands / to tell odd stories," which suggests handwork, craft and storytelling that no longer count for much in a world built on machines and profit.
The ending is the strangest part. People "come to be tin / and ring," as if they turn into the metal and sound of the factory, hard, cheap and clanging. It could also hint at coins, since tin rings like money. Either way, human beings are being turned into material.
The mood is wry and a little bitter. The speaker doesn't shout, but the short lines and odd phrasing leave a cold, uneasy feeling about what progress costs ordinary people.