What does Ezekiel 22:18 mean?

Human, the people of Israel have become like worthless slag to me—like the leftover dross from silver, copper, iron, lead, and tin in a furnace. They're all just waste. Ezekiel 22:18 - Modern Text Bible

(God compares the people to the useless byproducts left after refining metal, showing how far they've fallen from what they were meant to be.)