He didn't rip the soul out of them, he presented them largely as they were. Marston's Amazons body shammed women because that was acceptable back then. The fat Amazon Mala faces in the Contest is called Fatsis for God's sake, and she refers to her as a tub of lard. The athletes from Man's World that competed against them were drawn as more muscular and less conventionally beautiful, and it was shown that the more beautiful Amazons were superior to them because they were stronger while keeping acceptable beauty.
They also do not come from a culture where obesity would be a thing. Of course they'd react to it with alarm. PC anti-body shaming is not something they would know about, and Etta is right to call them out on it to an extent.
They succeeded with reforming people with brain washing all the time in the Golden Age...is that really a good thing? Sure Paula consented in the original stories, but a lot of others did not, and it was presented as being 100% good because that's what Marston believed. Morrison, and likely no modern writer, believes that brainwashing is a good healthy way to reform someone, which is why it has an unsettling air about it and not much different than Psycho's treatment of Diana. They just covered up the dirt. If Marston's Amazons' reformation techniques weren't incompetent, it's largely because he did not allow them to be and presented them and Queen Desira as being in the right, when it's kind of dicey if that should be the case.
We'll have to see how Diana continues to reform Paula in the third volume. Maybe she will abandon the Venus Girdles?