I've heard it said that Marvel has enough A-list female characters already that it doesn't need a singular "Wonder Woman," and that this is a good thing because it spares any single character the responsibility to stand for all women and be some kind of all-encompassing paragon as Wonder Woman is often called upon to be.
Sounds like a rationalization on Marvel's part. It's pretty obvious they want a successful female character along the lines Wonder Woman.
It didn't come from Marvel. IIRC, the sentiment was expressed by feminist comics critic Kelly Thompson. In 2010,
she wrote:
So Wonder Woman (both the character and the book) keep getting saddled with this heavy burden of being all women all the time, and of embodying perfection. But because there are seemingly infinite marquee male leads in comics – Superman, Batman, Green Lantern, Flash, Captain America, Iron Man, Thor, Wolverine, – you can take your pick, and they can all signify different takes on heroes in comics. But when you boil it down there is only one long running marquee heroine in comics – Wonder Woman. So she has to cover ALL the bases – and it’s just too much load for any one character (or book) to bear, and she’s constantly buckling under it. It’s impossible for Diana to be all things to all people and it’s the primary reason I think that she (and her book) are so often considered a disappointment despite the brilliant creators, writers, and artists often at the helm.
She's also spoken positively about the strong slate of female heroes and creators headlining Marvel books lately, and been very critical of DC's continued marginalization and sexualization of most of their female characters. Although I'm afraid I can't find a quote to back up what I recall her saying about Marvel's heroines not having the same "every woman" burden as Wonder Woman -- I can't remember the right search terms -- so I can't guarantee that my recollection is accurate. But it's absolutely not a statement from Marvel itself, I can assure you of that much.
Susan Richards is regulary portrayed as the most powerful member of the team as well as team leader whenever Reed is out of the picture.
She coordinates the logistics and handles and personel issues of Reed's scientific endeavors and charitable works and handles all of the business aspects of the operation that Reed is too busy for on top of being a supportive team member, wife and mother.
...
While I agree that an Invisible Woman solo movie is extremely unlikely to happen (as she is too closely associated to the team), don't simply dismiss the character as a housewife with super-powers.
In the Jonathan Hickman run, she's also a world-class diplomat, the person that the various non-human nations on Earth (like Atlantis, the Inhumans, etc.) turn to when they need someone to negotiate peace in the most delicate and dangerous situations. Oh, and I think she's Atlantean royalty somehow.
Not to mention that she's the mother of the most powerful mutant child on Earth and a 3-year-old girl who's even more of a supergenius than Reed Richards. Even aside from what that says about her own genes, she'd have to be an extraordinary human being to handle children like that.
The thing is, I can understand why people who don't currently read the comics would have a low opinion of Sue. She was originally a pretty weak character in the '60s comics, and many of the cartoon and film adaptations have been closer to that version. (Though she was the most impressive element of the generally disappointing
FF: World's Greatest Heroes cartoon from 2006.) But in the past few decades she's grown into a character who is every bit the Marvel counterpart of Wonder Woman in her power, poise, diplomacy, empathy, and ferocity in defense of those she protects. Yes, she's part of a team, but more than that: She's the head of a family, the anchor that holds it together. And that is a source of power in its own right. I understand the desire for solo heroines who can headline their own movies, as a counterpart to all the solo male heroes out there; but solitude is not automatically strength.