And then there is politics and plain old greed
Which get in the way of objectivity for economic theories. Say you are in government and you have theory A and B. Both sound reasonable but have conflicting results. Results of theory A favor the wealth of my group, or those that have financed my election, or those that can provide me a comfy and well paid chair somewhere when next election turn me out of government . Results of theory B does not. Guess one which I'm going to apply?
Basic failure of macro economics is that they fail to model one basic component of human behavior: greed.