The trouble with that logic is that there's a huge correlation between happiness (https://worldpopulationreview.com/country-rankings/happiest-...) and GDP per capita.
Besides, the inventor of GDP warned against using it as a measure for policy making, but as with many things in human affairs, oversimplified things that give an impression that helps manipulative people is just run with, regardless of the insanity of it.
BMI is another good example of not only a useless, but even more damaging and dumb fake metric.
But it does serve as an often-indirect measure, as part of a plethora of other measures, to simply explore the effects of policy.
I’m not aware of policy that focuses on improving GDP per se (not saying there isn’t any, Im just not that tuned into politics) but I am aware of people criticising their government when GDP has dropped after a major change. That’s the appropriate use, though.
[0] https://www.cbsnews.com/news/money-happiness-study-daniel-ka...
There is even correlation with my happiness by the minute based on some of the dumb things I read on here at times.