Economics is a science, or at least would be if done right.
Science is about predicting, modeling, and understanding the real world. Economics is the real world.
The "problem" is that it's a messy science with lot of variables, including human behavior. It's also difficult to get something close to controlled studies, as each situation is a different combo of factors. But this is also true of cosmology where we can't reboot the universe to try different things: we have to observe just the one we got.
Just because it's a difficult science does NOT make it a non-science. Nobody said science has to be easy to be science.