I’m in the same boat, a client of mine went and built their site on WordPress, now they actually need CMS functionality I’m struggling to build it on.
WordPress is fine as a Blogging tool, but it’s lacking the modular approach of something like Drupal, where every page request is routed through a front-controller and modules have the ability of implementing a menu hook. See: https://api.drupal.org/api/group/menu/6
Honestly, I’m thinking that the problem is just my ignorance, but if that is the case I can’t find anything in the documentation that shows the right way to route page requests.