Later civilizations disapproved of Homer because "he told lies about the gods." Look in Book 21 for some of these "lies." List and describe several of them in detail as they are presented by Homer. Do you think Homer actually believed in gods such as he sang about? If so, do you think he was being impious to his gods? Why or why not?
The later civilizations mentioned in the question are actually some of the Greeks who lived after the time of Homer. The most famous of the Homeric critics was Plato, especially in Books 2 and 3 of the Republic.
One of the critiques against Homer leveled by later Greeks was that Homer causes the gods to take on human form and qualities. Look for examples of this in Iliad 21 (e.g., Achilles' battle with the river). Later Greeks wondered whether "real" gods would actually behave like humans. Do rivers really get mad at people?
Another aspect of Homer's portrayal of the gods that later Greeks criticized was the gods battling and ...
This solution muses on the question of whether Homer actually believed in the gods he describes in the Iliad or whether he was being impious in his descriptions of them.