Mathematical structures are universal and some of them can be used as a box of tools for some sciences.
The problem with String Theory is that it is a machinery that takes a very long time to handle for the average PhD physics student. When you have been struggling with the mathematics for several years it still does not give you a nice answer as the equations are very difficult to calculate. We need a Witten II that can provide some insight and exclude some of the possibilities that so far are possible in String Theory.
Until that person will materialize my advice to a young PhD candidate is to stay away and go into some other fields of Physics. Note, I am not saying that String Theory is wrong, I just do not know.