It's probably that the controller and action for your plugin aren't set
up right. The way SimplePages does it, everything goes to the controller
in /controllers/PageController.php (from the 'controller' => 'page' info
in the array), and the function in it showAction(). That then digs up
the actual page data from the id and displays it.
So, chances are that you'll want to look at how your controllers are set
up, and compare with SimplePages.
Also, what kinds of features are in your pages? It might be that just
using SimplePages and maybe creating special shortcodes for your
functionality would be quicker and easier.
Patrick