The actress, who portrayed lawyer Miranda Hobbes on TV and in two spin-off films, admits the show doesn't adequately represent New York City, as the cast was mainly wealthy and Caucasian.
"I was always troubled by how undiverse it was," she tells Grazia magazine. "Certainly racially but also how the slice of New York City it was showing was so incredibly affluent."
Cynthia notes the series, which also starred Sarah Jessica Parker, Kim Cattrall and Kristin Davis, did feature at least one realistic character - struggling bartender Steve, played by David Eigenberg.
"Miranda's husband was the only representation of anybody who didn't have money for days," she adds. "I guess Carrie (Parker's character) didn't have money for days but you would never know it by the way she spent."
Despite her grievances, Nixon insists she's still "very proud" of the show.
"I love it dearly," she added, while insisting a third film will likely never happen, following reports of a rift between Cattrall and Parker.
"We've pretty much confirmed that's not going to be happening," she explains. "That ship has sailed."