Megaprojects are too small. The Manhattan Project didn't have its effect on the shape of war in its purview, the Apollo Program did not question the value of one-upmanship vs the USSR, the Three Gorges Dam did not concern itself with the decision making process for the industrial consumption of its electricity.
This requires thinking on the scale of planned economies, geopolitics, and ideology. We have to dismiss GDP and profit as a measure of success and find measures that indicate long term stability; to redesign the mandate and authority of the UN and IMF to liberate the global south and workers around the world from a life of miserable neocolonial overproduction; to choose a shape of laws and education and social norms that stops promoting overconsumption and focuses on the best things in life being free.