But is it as mythically important that a sandal-wearing goatsherd from Helmand province (AK-47-totting or not) gets punched in the face by Just a Kid from Brooklyn?
What about Captain America punching civilians in Sarajevo, as the Sarajevo TV building is being bombed in the background?
Iraqi soldiers confronting the invasion of their country by the US army, being punched in the face by Cap?
Cap punching little Vietnamese women and children in My Lai?
What I mean is that the world itself has changed quite a bit since the time of the Nazis. In terms of dramatic evil, no modern "bad guys" can do unambiguous, demented evil as well as the Nazis used to. And the good guys don't look that unambiguously, selflessly good themselves anymore, either. In fact, if you ask me (and I'm a westerner) they look more and more like the bad guys themselves.
Maybe comics can't just go on pretending the world is all black and white, when most of us can see around us that this is not the case.
The Nazis were complete shits on an unprecedented scale, but there was quite a bit of "demented evil" done by Americans too in WWII, like carpet-bombing European cities and interning citizens of Japanese ancestry.
The world has never been simple. "Black & white" is always a result of hegemonic propaganda more than actual conditions. It so just happens that certain strains of propaganda seem particularly ineffective on the most creative personalities of our age; but it takes very little for things to change. A lot of stuff produced in all media between 2011-09-11 and 2013-03-14 was very black & white, and without that senseless invasion we'd probably have many more monodimensional "Arab baddies" around today.
The film was set during WW2. If you portray Captain America punching Iraqi soldiers in 2004, well yeah your film deserves to fail.
Now, I always think this, but I think we also need some amount of moralizing mythology to remind us that, at the end of the day, when the time comes to act, there really are such things as good and evil. My favorite superhero movies tend to be the ones that show it, rather than trying to add "complexity" by actually removing the mythic content by invoking gray-vs-black morality and calling it "complexity".
Captain America: the First Avenger did it well, though I'd have liked them to have kept the Red Skull as a loyal Nazi. Let Hydra genuinely be portrayed as a Nazi cult, carried from its origins in WW2 to the modern day. It's mythically important that a Nazi piece of shit gets punched in the face by Just a Kid from Brooklyn.
It's mythically utterly unimportant that one manic-psychopath and another brooding, resentful psychopath "can do this forever" (The Dark Knight).
It's moral complexity when a fortunate kid from Queens tries to find some responsible way to deal with a working-class villain just trying to make it good in a world dominated by the Tony Starks and Thors (Spiderman Homecoming). White versus mid-light gray (with a good reason to be gray) offers us a compelling conflict, in a way that "two pieces of shit fight each-other" does not.
(Yeah, Marvel > DC, and holy war upon anyone who says otherwise.)