You are actually 100% correct. But not for the reasons that you think. And the SJW’s would freak out if they were ever told what is really going on there. Because it gets to the core differences between boys and girls, going back to toddler ages. And it very clearly indicates that yes these is a difference between male and female, and the comic product produced by them will by biological nature be substantially different.
Let’s step away from comics for a moment and talk about toys. We all know how the SJW’s have been claiming that there is no such thing as gendered toys. That kids are the same and boy and girls play is environmental behavior. So there should be no pink and blue toy aisles. The great claims that little boys and little girls are the same and interchangeable. And there are all sorts of “Academic Studies” supposedly claiming this. (Often Swedish). These studies are all badly funded and based on extremely small sample groups. 20-30 kids tops.
Well back in 2012 Lego, the brick people, looked at the wreckage of 25 years of failing to sell toys to girls, and decided to find out why. So they formed a research department and decided to find out how kids play. They poured tens of millions of dollars into it. Sample sizes were 10,000+. They spent 2 years researching. And then they published an internal top secret report on their findings. In 2015 Lego lent from the #3 toy maker to #1 by a broad margin. Their products were on fire. Their newly released Friends line for girls was selling faster then they could produce it. While every feminist and every media rag bitched and moaned about how horrible it was.
Now Lego’s actual reports, their research, is a top secret. An actual accurate study of how kids play is a license to print money for a toy company. It’s the secret formula. But they have spoken a little bit about their findings;
Core to what they found is past 3 or 4 boys and girls play very very differently. One of the biggest differences Lego noted was how each plays with the mini figures. Boys become the character of the figure that they are playing with. So if a boy is playing with a Spider-Man figure, he the boy, becomes Spider-Man. Girls project themselves into the figure. So any figure the girl is playing with becomes the girl. And making the character resemble themselves is important.
See where this is going. Boys take on the persona of the character being portrayed. Girls project themselves into the character and change the character to match and reflect themselves. Got that? Now go read OneManBlinds post again, keeping that core biological play instinct in mind. See the pattern? See how the same thing is occurring. And it is likely a huge part of the dissonance. Comics are at heart very much a boys form of storytelling. And while the female writers may be very good writers, stepping into that boys storytelling while telling it as a girl creates that subtle dissonance that results in the dull cardboard stories we see. They can’t help but project themselves into the toys, the characters. But that doesn’t work for comic characters. It kills them. The reader needs to be able to project the character into themselves. But nobody wants to project Kate Leth or Chelsea Cain into themselves. That way lies madness and alcoholism. But we’re not allowed to point this out because Muh Soggy Knees.
Well, yes and no.
See, a lot of modern marketing research and development is founded on a concept that was formed in the 80s referred to as Hyper-Serving the Psychographic. Which is basically a fancy way of saying "you pick a demographic that you want to cater to, create a broad psychological profile, and then pander to that broad profile x1000."
The end result was, especially with toys, was that companies developed extremely exaggerated, if effective, versions of toys that cranked up every feature to 11 - even in instances where at the core they were the exact same toy but with different visual like Polly Pocket and Mighty Max. Take your LEGO example for instance. It doesn't take a rocket scientist or several million dollars in research to understand that the reason the Friends set became popular was because girls on average are more interested in the appearance (particularly the outfits) of the figurines, so it makes sense that they would make the figurines bigger to allow for more detailed outfit options, nor that the sets are decided more mundane settings because they're also on average less interested in action. But everything else beyond that is just kind of salad dressing to the core elements, and don't really have any grand effects on the success or failure. So when The Chart Says the presence of pastries and color pink increases demographic interest by 3%, you can bet your ass a toy company is going to create 10 bakery-themed expansion packs and spray paint every single part a different shade of pink to cover the whole pink spectrum.
But the other part of this is that the key word to the above is "on average," and marketing research for entertainment is a little more complicated and overall tends to ignore deviations for the above reasons. I think a closer comparison to the current state of Marvel is when the creator of Green Lantern: The Animated Series
spoke about his experience sitting in on a focus group test of the episode. While the research did find that girls were more interested in the interpersonal drama and boys were more interested in the external conflicts and fight scenes, the research also found that the presence of one did not deter the enjoyment of either demographic as the overall enjoyment and investment was extremely high by the end of the episode. Because the thing that SJWs don't get is that, while men and women on average have different tastes, the ones who do enjoy things like superheroes either aren't bothered by the elements that aren't designed to appeal to them or actively enjoy those elements.
As for what all this means for Marvel and comics, I think there's been enough bad self-insert Gary Stus being written by dudes - Gay Ice Man, Squirrel Girl being used as a thinly-veiled mouthpiece for Ryan North's uninformed opinions on cape comics, the main character in Border Town, Bendis, Lady Thor - that I don't think the core issue is as simple as "female writers are stepping into Boys Territory and their female brains can't help but insert themselves instead of focusing on characters and story." After all, there's quite a few female writers that have gone unmentioned in this thread or have been praised because they actually like the genre and their merit speaks for themselves. It's more we've gotten a large influx of hipsters of both genders who don't actually like capes, and are instead trying to turn the genre into something else that appeals to them, which in turns off the core demographic - including the women who actually enjoy cape shit.