I've just started trying to put a DNN site together and I'm sensing there are pieces missing in DNN to pull this all together, and I started wondering - is Microsoft helping the DotNetNuke community at all? Or are they leaving it out there to languish?

In some ways DNN is somewhat "incomplete" but many of those holes are being filled by new Core features in Community Edition and added extensions in Professional Edition.  One thing to remember is that when you look at some other applications similar to DNN they are typically content management applications.  Dotnetnuke, however, is a framework used to build dynamic web applications.  These applications may be simple websites, but they can also take full advantage of the extensibility of the framework and become rich and dynamic web applications.  The ability to easily implement specialized extensions, or develop your own custom extensions, really unlocks a whole lot of power.