“fathers.” Not just the people’s immediate fathers. Here, in typical Semitic idiom, “fathers” means ancestors, and the ancestors were “no more,” they were dead. The Jews had been sinning for centuries, and the Babylonian captivity was a consequence for that. It is a sad reality that in many cases, some of the consequence for other people’s sin often comes upon those who do not deserve it or do not deserve the full force of it. Life is not fair in that way, but that is the reality of life.
“bear.” The Hebrew word often has the sense of suffering under a burden, and that is the sense here. The CEB tries to catch the sense of the text: “Our fathers have sinned and are gone, but we are burdened with their iniquities.”
“iniquities.” The Hebrew text has a word that means both “iniquities” and the punishment for iniquities. So, in this context, “iniquities” are also being put by metonymy for “punishment.” The children were bearing the iniquities and the punishment that their ancestors should have received themselves because they were the ones who sinned. However, Jeremiah’s generation was sinning too, so what had come upon them was not all the fault of the ancestors. The people of Judah were sinning too. However, it often happens in historical and/or spiritual settings that an ancestor does something bad that later affects the children. The NET text note speaks to the vocabulary in the verse and says, that the Hebrew word translated as iniquities “...has a broad range of meanings, including: (1) iniquity, (2) guilt of iniquity, and (3) consequence or punishment for iniquity (cause-effect metonymical relation). The context suggests that ‘punishment for sin’ is most appropriate here.”
Here in Lamentations 5:7, Jeremiah admits that sin is the cause of Judah’s problems, but he does not specifically admit the sin of his own generation, but he does at other places (cp. Lam. 5:16; and see commentary on Lam. 1:5).