The sexist part is the implication that every man is "bro" somehow... that only a female CEO could count as a symbolic change in leadership.
And an "unquestionable" symbolism is not the same as "the only possible" symbolism.
There are undoubtedly many things Uber could do that would be "unquestionably symbolic." Hiring someone else with a history of sexual harassment would be unquestionably symbolic. Nowhere did anyone say that hiring a female CEO is the only unquestionably symbolic act they could do. But it is one of them, and in that hypothetical instance, the symbolism would be positive.
And no, it isn't the only unquestionably positive act they could do.