Arnold Kling, in addition to his insightful series of lectures on macroeconomics, has written a brief history of macro-econometrics. In this history, he points out that most macro-econometric models embody strong priors of the model builder and that the forecasts need constant fudging to avoid being laughable. Here is his conclusion:

We badly want macroeconometrics to work. If it did, we could resolve bitter theoretical disputes with evidence. We could achieve better forecasting and control of the economy. Unfortunately, the world is not set up to enable macroeconometrics to work. Instead, all macroeconometric models are basically simulation models that use data for calibration purposes. People judge these models based on their priors for how the economy works. Imposing priors related to rational expectations does not change the fact that macroeconometrics provides no empirical information to anyone except those who happen to share all of the priors of the model-builder.

If we have to "adjust" or "adapt" our models with new data and new variables according to our hunches and priors all the time, it does cast some serious doubt on the usefulness of the models.