The key word in your gripe is
replace. That resounds more as an emotionally laden rhetoric then evidence of any actual fact by any means.
"You want to feature a POC character? Don't replace iconic folks. Make your own character and give us a reason to like them based on their personality and motivations and not the color of their skin."
That's exactly what they did however?
Iron-man didn't inexplicably transform into a black woman (creepy and weirdly misguided as that sounds). This is a whole new character, who happens to be an African woman.
She's not Tony or Ironman, she has an entire separate existence from Tony and he still exists. In other words, for people who like African Ironwoman, good on them, and for fans of the original comics and on-going comics of Ironman, he's
still there too. They both exist concurrently and haven't gone away or been replaced by any means.
So what's the issue here?
Why is that so offensive to you exactly? Maybe you're bigoted or, more likely, you find it easy to politicize it, but that doesn't make minority characters introduced a new phenomenon with some ultra-biased agenda. In 1999, batgirl was crippled and replaced by an Asian batgirl (Batgirl was crippled at the time, so two new batgirls were introduced). In the New 52 a black flash (Wallace) was introduced. Throw in John Stewart (African Green Lantern), Aqualad the black protege of Aquaman, Miguel, a latin american spiderman, and know this goes on thru decades. It's not new. Replacing iconic characters, do you know how many Robins and Batgirls, Flashes, Green Lanterns, and Spiderman's there have been? (Literally dozens and dozens of Spidermans, to the point where they had a whole arc about crossing over them all) Supergirl was introduced as a counterpart to Kal El. Wolverine had a female doppelganger cloned of him. Iconic Villains like Green Goblin and Venom might as well have been "replaced" numerous times with variants, did you even know which character holds the title and identity? I don't.
The character's "personality and motivations" are not based off the fact that they're not white, by any means. There can be an argument made for the lack of originality, but considering how Iconic superheroes get replaced all the time, it seems telling that you're only focused on this instance because this time they happen to be female
and black and that upsets some kind of standard you're 100% committed to. Long before any big political upset this has happened, which makes it seem like you're only projecting into things you're dissatisfied with.
Maybe you're not racist. But the fact that you consider a narcissistic hack Anita Sarkeesian like "the face of modern day feminism and equality" tells me that you're pretty biased and misinformed, and it's hard to have any objective debate with someone who considers "an African woman" superhero an offensive affront to them makes it hard to not assume some bigoted premise on your behalf.