It's interesting to hear hard scientists - physicists, chemists, engineers, etc. - critique the social sciences for lack of scientific certitude or rigor. "Psychology isn't real science" or "Economics is a pseudoscience"; I hear the remarks quite a lot and get frustrated when ever I do.
Social sciences don't have the same luxuries that many hard sciences do. Since social sciences study human behavior and systems, its very difficult to arrange controlled experiments - usually due to financial or ethical reasons - so teasing apart causality from correlation is a significant challenge. For example, economists can't randomly assign children to different levels of education during their lives as an "experiment" to determine how more schooling may impact career outcomes. Most of the time, they can only build sophisticated statistical or econometric models to find relationships in the observational data. Even controlled experiments with humans require careful experimental design and ethical precautions, an additional challenge many hard scientists don't encounter.
Economists don't always forecast economic downturns or make the best policy decisions. The saying goes "ask five economists a question and you'll get five different answers." But let's not forget that, like many social scientists, they have a difficult job to do. They are studying complex human systems under often chaotic and irrational influences.