The problem with "meritocracy" has always been that so many of its proponents never define "merit". Often they don't even have a specific definition in mind; they just know it as a term that's aligned with other parts of their favorite ideology. Sometimes they do have a definition, but also know that it's too obviously tied to legacies of inequity and discrimination. Nobody likes to
admit that they're a neo-feudalist.
True merit is hard to define and even harder to measure. As another commenter has already pointed out, that measurement has to include challenges and circumstances overcome. Unfortunately, those don't easily reduce to numbers. Sure, we can measure income or wealth, but how do we measure the impact of being denied opportunities to prove oneself? Of being dragged down by family and friends who need help because of the discrimination they also face? Of living in a place with poor schools, poor food, poor health care, for the same reasons? Note that some of these can apply to (especially rural) white people as well as others, but they remain hard to measure.
All we're left with is statistical measures and proportions, which will inevitably result in some errors. No matter what policy is enacted, those errors make it easy to complain about quotas and tokenism. Responses are possible, but less compelling. So we end up back to the fake meritocracy of grades and test scores. "What can we do" say the people who have already benefited and will continue to benefit from a system that ignores systemic inequality.