We could call it something like GDP and we can point to it anytime anyone says anything about anything, because we have taken the entire human race and all of its myriad components and put it inside that number. Nothing matters except the GDP number.
I'm so smart honestly I'm surprised nobody has done this yet already it's such a good idea. I can prove I'm smart because GDP goes up so that means I'm smart
Why would anyone take your idea seriously when they could just critically look at the facts and come to their own reason-based conclusions? It'll never catch on.
Mostly because thinking is hard. I mean it's not that hard but, it is harder than not thinking.