WordPress is very oriented towards being a “blog”. It’s very good for that.
By this, I mean that it mainly focuses on a single list of content which is time oriented in nature. Your posts, basically. It has added functionality to this to allow for other things, but this is the main focus.
-Pages are posts but without the time orientation.
-The Bookmarks (Blogroll) is essentially a list of links with attributes.
You can heavily customize it and fit it into any of several needs/designs because of the theme separation, but internally, this is how it’s organized.
It wouldn’t fit well to build, for example, a large scale sales site. Sure, you could actually do that with it, but it would be difficult and overly time consuming. There are better ways to do that sort of thing.
So WordPress is a special-purpose CMS, in a sense. It has functionality that fits it well to some needs, but not to other needs. Joomla is the same way, as is Drupal, and as are all CMS packages. They each operate differently and thus fit different things in different ways. You focus on what you need for the site you are building and pick the best fit to that. No one package, not even WordPress, is going to be the best fit for everything.