> Presumably, a process of trial and error will be needed to find the right choices

This is a huge difference between macroeconomics and thermodynamics. You can't just have a control group of people, test a policy with them and say 'omg they died of starvation'. I know well designed experiments exist such as basic income, but I hope I made a point: You can't just test macro policies as you would test heat transfer in a lab.