I think you may be doing economics somewhat of an injustice. There is certainly a lot of politics and some unfounded conjecture too, but in many cases it is the social "science" that manages to use formalization to reach real conclusions. Macroeconomics concepts such as "stimulus" are usually the example of the bad kind. But a lot of economics, especially microeconomics isn't.
There are real usable conclusions that have come out of economics too. For example, the idea that trade is good for both parties has been largely adopted thanks to the formal arguments that eventually won over the majority of economists. This goes back to Adam Smith and David Ricardo. The idea of floating exchange rates comes from economics departments and it has prevented a lot of currency catastrophes.
It's still social science and it's asked to provide answers for questions that it can't answer.
Pickety's ideas are interesting and so his his data. But, they are still new and in debate. Perhaps they hold some lasting insight into long term changes in wealth disparities, but the jury is still out from an academic perspective.