Yahweh wants Jeremiah to think deeply about what the people have said. This rhetorical question can be translated as a statement. Alternate translation: "You should have noticed what this people are really saying when they said, 'The ... them.'" (See: [[rc://en/ta/man/translate/figs-rquestion]])
Sight is a metonym for thinking. Alternate translation: "they no longer think of my people as a nation" (See: [[rc://en/ta/man/translate/figs-metonymy]])