Yahweh uses a question to express that the people should have left the city. It can be translated as a statement. Alternate translation: "This famous city once caused me to rejoice, but now the people should leave it." (See: [[rc://en/ta/man/translate/figs-rquestion]])
Some Bibles translate this with the people of Damascus speaking. Alternate translation: "The people of Damascus say, 'The famous city, which once made us rejoice, is now empty.'"