Another day, another messboard topic...
________
With respect to post-WWII gender roles, the first thing I think of is that when the war ended, the surviving American men returned home expecting to return to their status as family breadwinners, while women who had substituted for them in factories et al would return to being homemakers. Some contemporaneous women expressed the same sentiment. Some, like Betty Friedan, did not, and so we got the rise of second-wave feminism.
How did that affect depictions of men and women in postwar movies? I agree with the general proposition that one major trope to come out of the changes was "men have become weak and there's nothing that can be done about it." That's where your example of INCREDIBLE SHRINKING MAN (and the Matheson novel published the previous year) belongs, and there are surely others in the same vein.
However, we also get the trope "men have become weak but with the right approach they can re-assert themselves." I don't recall the specifics of REBEL WITHOUT A CAUSE, but it's strongly suggested that James Dean is messed up due to his mother, and near the end the father puts his foot down and reasserts his authority. HILDA CRANE (1950) spends most of the movie with Joan Crawford manipulating her husband, but then he walks out on her at the end. You can also see this type of trope in a fair number of stories predating America's entry into the second world war, not least the 1936 GONE WITH THE WIND novel.
The movie we're discussing, DAUGHTER OF DARKNESS, is a little different, and it's also not precisely "postwar" since it's based on a play performed the year before Britain entered the war against the Axis powers. It's not that the men in the DOD movie are weak, but they're unable to deal with the ways women think and interact, which constitute a separate social world. You see the same ethos in the 1939 Bette Davis weepie THE OLD MAID, which came out the same year as the GWTW adaptation. The world of men there just barely impacts on that of women, even though the story takes place against the backdrop of Civil War violence.
ANGEL AND THE BADMAN is a different trope still. John Wayne's bandit character is never weak at any point in the story, but he's a creature that needs to be civilized by the gentle Quaker girl, who takes him off the path of doom. That too is a very "woman-centered" ethos, though it doesn't depend on nullifying masculinity, as does HILDA CRANE and maybe REBEL.
There probably are other movies, not least SF-genre films, that get into the trope of men falling victim to either too much or too little masculinity. You mention NEANDERTHAL MAN, and MONSTER ON THE CAMPUS might be another example of the latter. But I find it interesting that in the late forties and fifties we start seeing a fair sampling of low budget "action girl" (often swashbucklers) and "monster girl" films, far more than I think one can demonstrate from the beginning of sound films through the end of WWII-- and DAUGHTER OF DARKNESS is one of these. But whether that indicates a real shift in genuine gender roles would be food for a second discussion.

