That sounds dangerously like pedantry to me. The point is not that the mathematical expressiveness of the network model is as powerful or more powerful than what you can do with relational stuff. The point is that the network model maps nearly 1:1 with the actual programming model used to implement the application logic.

All that relational goodness does you no good if you want to architect your application using an OO data model in a web application server. Maybe you're trying to argue that that's the wrong way to do web applications? But if you accept that people want to use Rails/Django/etc... then you have to also admit the argument that RDBMS's are the wrong tool for the job. This is true for the same reason that a Dremel is the wrong tool for framing a house, despite the greater expressive power of the Dremel's cutting tools.