What is the evidence that econometrics has empirical value? Economies are extremely complex systems with many variables, not to mention the fact that they emerge from the interactions of complex beings. I agree that economies have certain underlying principles, but I remain skeptical of the overall value of econometrics as a science.

A truly useful econometrics would be a valuable tool in predicting the future behavior of the economy, particularly in predicting shocks like the recent financial crisis and Great Recession. But it did not happen.

If econometrics can't predict the future, how do we know it even effectively describes the past? What is the evidence that it has empirical value?

Clarification

I regret any confusion this may have caused, but let me clarify what I'm looking for here. I regard this as an epistemological question. A better way to phrase it might be, "Can econometrics conform to the scientific method?" or just "Is it science?"

This is, at least in theory, a specific, answerable question, even if it is, as Alecos Papadopoulos noted in his answer, a matter of degree. (A view I share.)

This does not mean that specific examples of econometrics' successes and failures are not relevant.
To (slightly) paraphrase the OP:  


  Economies (Human Bodies) are extremely complex systems with many variables, not to mention the fact that they emerge from the
  interactions of complex
  beings (factors). I agree that economies (human bodies) have certain underlying principles, but I remain skeptical of the
  overall value of econometrics (medicine) as a science.
  
  A truly useful econometrics (medical science) would be a
  valuable tool in predicting the future behavior of the economy
  (human body), particularly in predicting shocks like the recent financial crisis and Great Recession (severe illnesses or near
  death). But it did not happen.
  
  If econometrics (medical science) can't predict the future, how
  do we know it even effectively describes the past? What is the
  evidence that it has empirical value?


Comment: There is a Present that needs to be dealt with, just like with human bodies.

To (slightly) paraphrase Milton Friedman:  


  I don't care how I predict, as long as I predict adequately.


Comment: But what do we do when our predictions are not adequate ?

Econometrics is based on Mathematical Statistics on the one hand, and on the assumptions made by Economic Theory on the other, which in turn are based on (imperfect) empirical observation, and are then led to their logical conclusions. In other words, Econometrics uses rigorous mathematics, induction, deduction and all the words dear to an epistemologist. Its epistemological foundations are solid as a rock.  

What hangs on the balance is the observed validity of its abstractions. So the question is not whether Econometrics is a science, in the sense of whether it follows the scientific method or not. It does, fully.  The question is whether its results are useful.  

But what are the criteria in order to determine "useful"? Is it just adequate predictions? That would be a matter of disagreement between humans.  

And is it a matter of a "yes/no" answer?  Or is it a matter of degree to which it is useful? In which case, we have to somehow measure this degree (after we have agreed on the criteria), which brings us back to where we have to collect, analyze, assess, and debate the evidence.