Compare WordPress vs. Joomla!
WordPress is not a very modern PHP CMS and does not use Symfony or other components. It is very popular and earns it's position in the listing of Symfony CMSes.
Joomla! is one of the big three PHP CMSes. Currently it uses only a single component from the Symfony project. Joomla remains a strong contender with a large number of users and extensions.
CMSes vailable for comparison: BackBee, Bolt CMS, Concrete5, Contenta, Contentful, Cosmic.js, Craft CMS, Drupal 8, eZ Platform, Fork CMS, GraphCMS, Grav, Jarves, Joomla!, Kunstmaan, October CMS, Open Orchestra, Pagekit, Pimcore, PyroCMS 3, Reservoir, Spress, Sulu CMS, Symfony CMF, Symphony CMS