Economics is a social science, just like anthropology, archaeology, history, linguistics, political science, psychology, sociology, etc. etc.
It's never going to be something with Laws of Gravity or the like, because humans are never wholly predictable or rational creatures. But that doesn't mean we can't come up with models that explain markets a majority of the time, in a macro sense.
Why do you think central bank policy has been able to prevent a depression from occurring over the last 90 years, when in the past they were a regular occurrence? That's economics in action. Just because it lacks the certainty of computer science doesn't mean you can throw out the baby with the bath water.