There are lots and lots of problems that are either unsolved or are being solved in ways that are less efficient and cost-effective than they could be, particularly outside of the consumer space. In many cases, these problems can be solved with relatively unsophisticated applications. But the folks who sit around thinking about the usual consumer internet suspects (Facebook, Twitter, Instagram, etc.) never discover these problems because more often than not, they have no domain expertise.
Sadly, it seems to me that many technical wantrepreneurs have no real interest in developing domain expertise because they believe there's more value in mastering the framework du jour than focusing in on a vertical and developing a real understanding of it over time.