I don't think you can look at her clothing divorced from the reality of American politics. It's just imposing yet another expectation on her.
Whether or not racism and misogyny stop her is different from whether it can be used to distract the voters. She's already being portrayed by the other side as deeply unserious, much of which centres around her being a woman, not to mention a non-white woman. Her laugh, the fact she dances, the fact she occasionally trips up in answering a question, an historical relationship (I have literally seen people on this site saying she blew her way to the top). The very last thing she needs is for people to be discussing her outfits. The tan suit, which was an homage to Obama's much-abused tan suit, was sort of an inside joke, and, I suspect, as far as she's going to go.
I will also say, that the rigours of an American presidential campaign aren't comparable to anything Thatcher, Condoleeza Rice, Theresa May etc. had to take on. She's constantly criss-crossing a massive country, across time zones, speaking to crowds, wooing donors and having to get up to speed on a presidential campaign all day every day at the moment. She doesn't need the distraction of thinking about her clothing. Yes, she'll have a team on the campaign coordinating, but one incident of the wind blowing up a skirt when coming down the steps of a plane and she'll lose 5 days of being treated like the serious person she is.
She also strikes me as someone who might not be terribly interested in clothes beyond functionality? Whenever I've seen pictures of her in off-duty wear, it's pretty unexciting - jeans, quilted jacket, converse hi tops. Being a woman doesn't necessarily obligate her to satisfy our interest in fashion.