On her own, Darcy isn’t bad. (In fact I think her actress is a babe and the character is a cute and quirky sidekick! I just don’t get her popularity beyond her value as a self-insert for many white women in fandom.)
What she represents, as fandom’s self insert potentially being inserted into Wakanda, is ridiculous. I’m not linking to the person because they’ve already been dragged within an inch of a life for it, but the response to that one person everyone dragged for their Darcy/M’baku post was kind of like “well, this better not happen again”.
The idea of using Darcy in a story/RP/headcanons centering her white womanhood in Wakanda (which is legit how fandom does it) is bad. Darcy doesn’t belong in Wakanda. That’s not me being mean or “reverse racist”, but like…
Literally, there’s no reason for her to be in Wakanda, much less in a relationship with a character from Wakanda who is absolutely uninterested in whiteness and white people.
Putting Darcy in Wakanda/in relation to Wakandans winds up with a focus on a white character’s feelings/narrative/etc over that of a Black one.
And since fandom can’t get that there’s no reason for her to be anywhere near Wakanda (much less the focus of a story set there)… “Darcy in Wakanda” gets her own square!