You can’t eat Gross Domestic Product (GDP), yet it is the indicator that economists pay closest attention to.
GDP gained currency during WWII as a way of keeping track of war production, and has since remained the dominant measure of economic output. More than that, it has become a byword for living standards.
Looking across countries, economic output per person, or per capita, adjusted for price differences is still a reasonable proxy for average material living standards. At least up to a point. It is not necessarily a good indicator of individual happiness, or of societal wellbeing, however.
The main problem isn’t with measuring GDP per se, but that maximizing it has become the over-riding target for economic policymakers. They have lost sight of the fact that increasing economic output should be a means to an end, not an end in itself. The over-riding priority should be to maximize the welfare and happiness of the greatest number or people while ensuring everyone has a basic, decent standard of living. Unfortunately, there is no consensus around how these should be measured.