Why is it "precisely the wrong approach"? And why does it have to be just one?

I agree looking at the quality of life of the poorest is a valuable barometer for the quality and success of a society to serve all its people. Similarly I think looking at the richest and what checks exist on their power also says a lot about the health of a civilization. It also makes perfect sense to me that we would look at wealth distributions as well. After all comparison and competition is core to the human experience, is entirely relative, and more visible than ever in the age of the internet and social media. These dynamics massively impact individual perceptions of success and political priorities, fairness being a deeply baked value in the human wetware (just ask any 5-year-old), so not sure why we wouldn't want to address them directly. Certainly there's more value than in the superficial tribalism and dog whistle culture that passes for political discourse today?