If Diana was taking on this mission to stop Germany's secret weapons thing, and she was making all their decisions, and Steve was just helping her out with intelligence information and advice, I feel that would've been very different, but that's not at all what happened, right?
It's been observed on the board before (sorry, I forget exactly by whom in what thread, though perhaps by multiple people; in a DISCO thread maybe?) that the events that are depicted in a story are the result of choices made by writers as to what to depict. Writers have to own everything that happens in their stories. There's no falling back on the idea that certain events must occur; things happen only because the events shown are what the writers want to be under consideration.
With that in mind, saying that Steve had to sacrifice himself at the climax of WW1 to teach Diana something about the goodness in mankind is a rationalization. As I said
upthread, "... there are any number of ways in which Steve could have proven to Diana by self-sacrifice that there is moral strength in mankind in addition to corruptibility." Ergo, if the priority is to show WW doing all the heavy lifting of heroics, then to accomplish that, they'd simply have to formulate another way for Steve to do it.
Here's a way it could have gone. Simply have Steve take a bullet fired at WW by Sir Patrick himself. Diana's back is turned to Sir Patrick because she doesn't fear him. But Steve has already come to suspect him due to some slip Sir Patrick has made earlier or even just before or because Steve can see the mask coming off just a little bit earlier than Diana can because Steve, as a person, has more experience dealing with people than Diana does. Diana gains insight into the human condition, because she herself has been fooled by evil. Plus, Steve's sacrifice echoes Antiope's from back on Themyscira (Paradise Island), so Diana sees that men can be just as good as Amazons. Diana can redirect some of Ares' lightening to destroy the bomber, and then she can redirect the follow-up attack powered by his outrage back into him, killing him for good. Voila. Steve's still dead, and Diana can withdraw from the world as before. Plus, there are a zillion other ways to square this circle besides this.
Now, clearly, I didn't have as big an issue with WW1 as you (
@Marynator) did about these things, or I would have noticed the issue before, myself. However, I always thought that Steve's self-sacrificing heroics were trite (their triteness is a general problem that transcends WW1), and I never liked the final battle with Ares. Of course seeing things from other perspectives is part of what I get out of discussion.
No one has brought it up before because its a bad, if not misapplied point not to be found in the film. As noted yesterday, in Captain America: The Winter Soldier, supporting characters like Fury, Black Widow and Falcon all had their strong moments and an impact on the story in a film that was about all about Cap (note: it was not Cap who killed Alexander Pierce--the real villain of the film), yet the fact that Fury and company played their strong parts did not take anything away from Cap at all. The same applies to Wonder Woman, where realistically, she could not be in every conflict save for the main one against Ares as seen in the film. Trevor's heroics served a very obvious purpose others seem to miss--it is his death and the experiences of a world rejecting peace that sends her into the reclusive mode set up in her future in Batman v. Superman: Dawn of Justice. I believe some are looking for some sort of problem in the handling of Wonder Woman as the lead in her own film where no problem exists.
The MCU movies represent a shift away from lone superhero films anyway, because in most cases other superheroes exist in each film besides the nominal main character. If Superman, Batman, or Aquaman had been in WW1 (the WWI part), I'd expect them to have done some of the heroic heavy lifting. But Steve Trevor isn't a superhero.
