Regarding boards, that's a bigger dissertation. "White male" is much too reductive, when there are certain kinds of people that have disproportionate representation on boards. Even the whole finance sector has extremely disproportionate representation from some extremely small ethnic groups.
So, what is the right number? Its more like a complete rebalancing would match "market realities".
The point of companies is to address a market, the point isn't to make people inside of it feel like they won the merit lottery on their own accord. A board should be able to identify and relate to the markets they need to address. If having a voice to more accurately tap into underserved markets is the stage that the company is at now (because it adequately serves the larger markets already), then it needs more than 1 person that has experience in those markets. Otherwise it will just get tone-deaf ads, tone-deaf outreach efforts, and risk getting cancelled from making huge misses.