That's irrelevant as far as the designation of "science" is concerned. This is a question of knowledge and certainty, not practical application. The point is that results in cosmology (and other fields) are very well confirmed despite the fact that they don't come out of strict experimentation. In that same vein, when someone denies that economics is a science I'd argue they're really talking about whether its results are robust, not whether economics uses a certain methodology or is put to certain ends.

No, you don't. But having the complex macroeconomics models far beats relying on layman's guesswork.

You've never looked at a macroeconomics model, have you?

Economics is complicated because it is modeling the behavior of human beings.

Math is easy, computer science is easy, modeling the collective behavior of humans is hard.