This humble corner of cyberspace has told you enough times, but don't take Otto's word for it...read somebody smart who knows what they're talking about. An extract:
"....(economics) is subject to three critiques:1) It helped cause the current economic crisis
2) It failed to see it coming
3) It doesn't know how to fix it.
In my book, that doesn't leave much out. A theory that actively causes harm, can't prevent it, and can't cure it is not much of a theory.