However, if one could describe a typical important crisis/situation in a significantly vague manner, you could perhaps get people to recognize an important problem in their life that they have been neglecting. Then, perhaps give some generic advice that, thanks to our brain's heuristics, brings a solution to mind.

That's basically the idea, yes. The forer effect might be used to make things emotionally salient in useful ways, but there definitely should be more to any given horoscope than that.