I don't know if it's so much not thinking things through as much as the idea that wonder woman delivering the final blow is just not something that could concievably happen in the minds of the writers.
I mean, this movie is kind of...overwhelmingly masculine. It's something I've kinda struggled to articulate, and
this article does a good job of putting it on paper about how it's toxic masculinity that ruins the film and everything (and there are other articles if you do a google search), but even going beyond that, stuff like Cross fit and the hyper aggression of the characters and the inability to talk things and how the suits emphasize the male physique more than any marvel movie or past DC movies and a lot of the language ("You're not a man" "He made me half a man") and so on just kind of makes it feel like this is a film that's just...for men, or atleast ones with an overattachment to their sense of masculinity.
As such, the very idea of a woman being the one to step in and fix things, even if it's the logical option, feels like its something the audience, or atleast the intended audience, would consider an insult, even emasculating. It's something that doesn't happen because it didn't occur to the writer, but more like it's something that just isn't in the writers creative vision to happen.