It's so weird to be complaining about the accents. It's a movie that takes place in ancient Greece, FFS; we have no idea what their accents would sound like if they were somehow capable of speaking modern English, since their entire culture pre-dates audio recording technology (and modern English, for that matter) by multiple millenia.

Seriously, people are just weirdly conditioned to the classical world speaking with a British accent for some reason, I guess.