I didn't really pick up on it when I watched the film, partially because, yes, there are other characters who serve a similar role, like Loki.
However, ask yourself: what are the female heroes doing in this movie? What are their roles?
Gamora is the most prominent one. Her death is the pivotal moment in the protagonist's arc. Nebula's main thing is being tortured, as part of the dynamic between Thanos and Gamora.
Black Widow's role is entirely forgettable. Okoye is more memorable, but only because she steals a couple of scenes.
Wanda's role probably has the most substance, outside of Gamora.
So it's really hard to compare Gamora to Loki, in the sense that all of the heroes who have prominent roles in the film are male. Starlord, Tony, Strange, Spider-Man and Thor, especially.
I wouldn't dismiss the film on that basis, and I didn't really come out of the theater thinking about it, but I can understand why some people might not be too thrilled with that aspect of the film. They really need some female heroes who actually play pivotal roles (Captain Marvel).
I think as dudes watching the film, we are less likely to notice or be bothered by it.
I do understand what you are saying; so please, bare with me what i'm going to say.
For me, in this film, I didn't view it as some number of Males vs Females in prominent roles. One of the biggest male character...Cap, for the most, role in this film, was just about as nonessential as Falcon, War Machine & yes Black Widow. Those four character really affected little to nothing, in the grand scheme of things...they where a prop, to get Vision to Wakanda...that effectively it. Yet, it worked...their role filled a need in the story...not every character, female or not, has to be in the forefront, to showcase some PC equal billing. They just need to fulfill the role they are given.
With that said...Gamora & Wanda had imo, a very prominant role, that I would suggest, rival the role given to Tony & Stephen. Imo, there was four main stories being told, sorry Thor fans.
1st: Love at all cost, by Vision & Wanda...it was poignant when Vision told Wanda, "you can't hurt me" when encouraging her to commit a deathly act...because that reminded Wanda & the audience, that he was a machine. At some point, i personally became so wrapped up in their affection & love that was on display, i forgot he was not human. That he was an android that felt these very real emotions...even stumbling of his feeling when trying to express them. So he reminded us all, dont fear for me, you cant hurt me...but countless could if she don't do it.
2nd: The Arrogant Geniuses that had to quickly learn to trust each other insight, over their own....their own knowledge & intellect. That was very hard for these two. If Stephen wouldn't have back down & take the fight to Thanos on Titan & did what he insisted, that they get back to Earth, pronto....there may never had been that one glimpse if hope out of the 14 million plus, scenarios that Stephen saw. Same can be said with Tony now having to trust what Stephen did, was the right course of action. He asked Stephen, "why would you do that?" Because its was the only way...as hard as that was for Tony to accept, because of his own instinct & intuition on just destroying the stone, like Vision suggested to Wanda, he realized what Stephen was saying...it indeed the end game now.
3rd: Father & Daughter...which for me, was the most poignant part of the whole film. Through all of her, Gamora, bravado, she was really hurt for what she thought she done, in killing Thanos in "Knowhere". That was truly a heart felt weep for a father figure she despised. Thanos was on point when he said, "so there is Love there." That made his heart grow even more for her. I suspect, had she not shown so much raw feeling for him, it may not have been "As" hard for him to do this drastic deed. Not saying it would have been easy...just saying, the Mad Titan heart wept as tremendously as well at the notion of losing her forever. He stated when young Gamora ask the cost...."Everything".
Finally: Thanos Quest...we have been told, this was Thanos movie...and it was; so, kinda goes without saying.
It will be interesting to see how prominent CM & Wasp role turn out & if BW become more essential. Neitherless, everybody did well in the role they had been cast & the part they play in the story.