If they want Carol to be their Wonder Woman, they need her to act the part.
Diana has the strong and sturdy body of a female warrior (Most of the time), but there are also qualities to her that are beautiful and delicate.
Part of Diana's appeal is that she shows she can play with the boys, but she never forsakes her traditional female qualities.
Carol is usually drawn with dyke hair and a boxy frame with little to no curves. The few artists that do draw her traditionally feminine, with curves and nice, long, bouncy hair? Carol looks fantastic even with the current uniform.
The other issue is just personality.
Diana has poise and dignity, but she also likes a good fight. She may have no qualms about killing people and flexing her muscles when someone needs intimidating, but she's also very kind and warm when she needs to be. Diana, for all her strength and power and unwillingness to back down, is usually approachable.
Carol on the other hand is often a militant bitch and often comes off as stand offish.
Diana is the heroine who finds a lost child, scoops them up in her arms, and personally brings them right to their parents and lingers just long enough to enjoy the sight of a happy family reunion with a smile on her face, giving the child a pat on the head, possibly a hug, and gives them some inspirational words on how to be a good person before flying off.
Carol drops the kid off at the police station and lets it be their problem.
And yes, Wonder Woman has her bitchy moments, but those are exceptions. With Carol, being a cunt is the expectation out of the gate.