It is not carrying a lot of weight. Macroeconomics are different from microeconomics. On a micro scale agents have enough weight on the system where a specific action might break a model. On a macro scale each individual agent's action carries less weight and therefore the system becomes predictable.

On a micro scale it is possible, and sometimes favorable, to intervene. On a macro scale to intervene economically becomes impossible due to the economic calculation problem. It is widely accepted in modern economics that the unit of maximum extent where economical intervention is possible is a business/company/enterprise. Or in sociological terms the maximum unit is the family. Anything broader than that and the compound effect of the economic calculation problem becomes apparent and inefficiencies accumulate. Autonomous decentralized mechanisms (like a free market) are the only solution to it, but not the most optimal.