And how does that critique the way women were drawn in Marston's original Wonder Woman? You can just as easily say it critiques the way women are drawn in comics today: even more slender, even more impossibly-bosomed, and even more attractive and sexualised.
When Etta calls out the Amazons on the way they treat her, she doesn't critique Marston, she critiques the Amazons as they are portrayed by Morrison. And Morrison set up his Amazons to behave badly.
Wonder Woman the movie arguably does a better job of critiquing Marston, and comics in general, here, by the simple act of making the Amazons come in several different forms and sizes.
Thanks for giving a reference on the orgy. However, the orgy in Morrison's description sticks out like a sore thumb for two reasons. First is that it is not needed for the narrative, it is only included to check a box for "weird stuff that Marston did". This worsens the issue with that it feels like an odd fit to the culturally and technologically advanced Amazons.
Marston, on the other hand, made sure there was a narrative reason why Wonder Woman was at the orgy, and he had done a lot more work in establishing both Diana and the Amazons.
In medias res is starting with the action first; it's not "show" as in "show, don't tell". Again, it is not necessarily bad to front-load details, if it is needed for the narrative, or for som dramatic effect. At the same time, the info-dump is usually treated as one of the common sins of writing. Morrison puts checking off weird Marston stuff before telling his story, and in effect gets too much exposition and background before the actual plot even starts. While it's not technically info-dumps, the result is largely the same. Now, he is not alone in doing so, and arguably it's a common flaw in every Wonder Woman origin story I've read since Perez. But it feels worse here, since Morrison does not so much tell a long backstory as checks of old Wonder Woman trivia.
That might be what Morrison intended, but I don't think he hits the mark. Where movie Hippolyta comes across as protective, Earth One Hippolyta comes across as smothering. Where movie Hippolyt comes across as sorrowful over Diana's choices, Earth One Hippolyta comes across as wrathful. Instead of accepting, she is crushed in the end.
And Medusa isn't extreme violence?
You're coming really close to the No True Scotsman fallacy there.
There have been plenty of critiques of Marston's Amazons, but they do so by looking at the background and trying to work out how the Amazon society would function and evolve, or by looking at the splits and tensions that would run through it. See "The Circle", or The Legend of Wonder Woman for great examples.
By placing the critique of Amazon behaviour largely in the mouth of Etta, the result is also to say that the women of Man's World (like Etta) are morally superior to the narrow-minded Amazons.
I'd also add that doing meaningful and deep in-media critique of other media is extremely hard, and probably even more so when doing it within the same franchise; often you will do good with simple re-examinations or exploring new angles or fissures. Ostrander and Yale did manage to pull it off in "Oracle: Year One". Even Moore arguably failed to do so in Watchmen, because the result by other comic book writers was to take it as a style guide rather that critique.