We can all debate whether America will elect a Black woman as president in the abstract, but will this electorate choose a sane, competent and centrist politician who is under the age of 60 instead of a convicted felon and chaos agent? I will take those odds.
Trump is unpopular. His policies are unpopular. He has never won the popular vote. His preferred candidates down ballot go down in flames. Democrats are on the right side of a highly motivating issue swing voters: abortion. Biden has struggled to take that fight to Trump. Harris won't.
Will black women deliver another close election to Dems right after Dems give them the symbolic finger in front of the nation? Seems like that might be an impediment to victory too. Especially since nobody else you could get to do it is meaningfully different on policy.