String theory is more analogous to quantum field theory than it is to the standard model. The standard model is a model of quantum field theory. Likewise, a theory of everything could potentially be a model of string theory. Particular models of string theory are ruled out by the same experiments that rule out particular models of quantum field theory. The ultimate goal is to find a model of some theory that reduces to the standard model in the low energy limit and includes gravity.

Now, it's potentially the case that string theory makes predictions for a given model that can't be practically tested. That's definitely an issue. Another issue is that we haven't yet pared down the possibilities in string theory to a parameter space that can be reasonably searched experimentally.

Social sciences do generate testable predictions, but they often run poor studies that fail to falsify untrue predictions. 538 recently had a good explanation.

http://fivethirtyeight.com/features/science-isnt-broken/

AFAIK string theory hasn't made any testable predictions beyond the standard model, but the standard model itself does have testable predictions that have so far all held up. So string theory is just as falsifiable as the standard model.

I don't know about the social sciences. That's painting with a pretty broad brush, IMHO.

True, and I was bit tongue-in-cheek as a social scientist myself. Replicability of many studies is a long-standing issue.