Joomla! and Wordpress are great content management systems and offer a wide variety of features that should cover most of the usage scenarios when you employ a CMS to build a website. If that’s not enough for your needs, you can choose from thousands of free and paid extensions (or plugins) that will, depending on type, either add that one small feature you need (that “Share” button for your audience to share some useful information from your website on their social media accounts), or completely transform your website’s CMS into a full-fledged social network, or news portal.