String theory is not a new, promising idea that needs time to develop. It has been around for about forty years, has been intensively pursued by thousands of physicists for about thirty years now. The end-result of all this work has just been a better understanding that the huge problems with the idea of string theory unification seem to be fatal. If you make the most optimistic assumptions about string theory unification schemes doing what they are supposed to, you end up with the “landscape”, a theory which can’t predict anything at all.
The basic problem with string theory unification research is not that progress has been slow over the past 30 years, but that it has been negative, with everything learned showing more clearly why the idea doesn’t work. The problem with progress in string theory as a function of time is not the size of the derivative, but its sign.