I was not proposing alternative metrics for measuring quality but I believe it should be safe to say that talk proposals are a better indicator of talk quality

I was not proposing alternative metrics for measuring quality but I believe it should be safe to say that talk proposals are a better indicator of talk quality than race and gender. Nor was I recommending maximizing individual speaker quality over maximizing conference quality. To reuse your two metrics, I would expect 10 different talk topics given by people of the same race and gender to yield more value to attendees than the 10 same talk topics given by people of all different race and genders.