In Chem the above statement = fail
In Physics the above statement = fail
In Computer Science the above statement = fail
Even in sociology the above statement = fail
Economics is littered with examples of "formulas that don't correspond well to actual data". Then economists run a massive economic experiment called Quantitative Easing with these formulas...
It is hard to impossible to gauge human behavior (which is what economics is primarily concerned about) with strict mathematics. Also, wrong premises will lead to wrong conclusions which would not correlate with empirical data. I don't see how economics is different in this aspect from any other empirical science that operates with and checks its models against empirical evidence...
Then it is not a mathematical formula is it? It is a very flawed approximation of reality that should not be used to run a massive experiment. Economics should be frank about this but it is not.
That's the whole problem: economics ignores the empirical evidence to achieve political outcomes. It's bamboozle with BS all the way.
It is still a mathematical equation
But now it seems I see your point. And you're blaming the wrong party here. Economics is a science, and as a science all scientific methods (techniques for investigating things, acquiring new and correcting prior knowledge) are fully applicable to it. As far as I know Fisher's formula has never been considered as an ultimate truth in itself, but only as a very rough approximation to real life economical phenomena...
It is surely not economics that you refer to here when saying that it ignores the empirical evidence to achieve political outcomes