Rapid-fire thoughts, with spoilers for a 3,000 year old story.
The movie signals quite early that it's not set in Ancient Greece, the historical place, but rather in Ancient Greece the mythological setting, and it's a stylized and opinionated interpretation of that setting as well. You'd think this might be obvious given the kind of story that it is, but a lot of the controversy around the cast seems to have overlooked this. With that in mind, a number of things that are obvious historical inaccuracies make perfect sense. Helen is cast as an extremely dark-skinned black woman because it makes her stand out visually from the rest of the cast (almost all of whom are white), which is the same reason that Agamemnon has that vertebra helmet.
Page is in the movie for all of three scenes, and for the character she's playing it makes sense that they wanted to cast a shrimpy twink.
Zendaya as Athena is... she's fine. She's also more minor than you might think given pre-release hype.
I understand why people were skeptical that Damon could carry the role of Odysseus, but in fact I thought he was great. With the beard and his weatherbeaten skin, he actually plays the role quite well, and was quite believable as both the grim warrior and the polymetis trickster.
Tom Holland feels very young as Telemachus, but I believe that this is deliberate: the central problem of the film is that he is fully-grown but has not fully become a man, due to his mother's perpetuar not-quite-widowhood. Hathaway is phenomenal as Penelope.
The film's moral universe centers around the Law of Zeus. I suppose this is loosely based on the actual Greek concept of xenia, but it is defined in the film with the exact words of the Golden Rule. A savvy viewer will note that the Golden Rule is, in fact, associated with not Zeus but some other guy who came several hundred years later. This bit of anachronism is fully deliberate.
The central problem that Ithaca faces is that it is a kingdom without a king. The Law of Zeus requires that the suitors be extended hospitality, even though they will not return this hospitality but are rather participating cynically as a way to exploit the palace in its kingless state. What Ithaca needs, and this is stated explicitly, is for the king to return and kick the unwelcome guests out, and properly restore the kingdom.
And all this happens in due time, and it is awesome.
The obvious political interpretation of this barely needs to be spelled out.
The main thing that Nolan adds to the story is the threat of the Sea Peoples and the looming Bronze Age Collapse. This is not something that exists at all in the actual Odyssey, but here it frames the whole narrative as a kind of tragedy. The king can return, and Ithaca can be made whole, but this does not prevent the turning of the age.