It is exactly as useful. Macroeconomics was completely tangled up until people understood that in a perfectly function economy there was be no business cycle,

It is exactly as useful. Macroeconomics was completely tangled up until people understood that in a perfectly function economy there was be no business cycle, that even a serious shock would only temporarily slow down the economy. So the focus turned to understanding the market imperfections that make temporary dislocations have such long-term effects.