I just started a new project on Contao 4 CMS and are a bit stunned by the absense of an easy "editor friendly" way to edit and manipulate the content.
Is there some kind of custom module which adds this "pagebuilder" feature as we know it from other cms systems like Wordpress or Drupal (with Paragraphs module)?
In Contao (all versions) the actual content of pages (i.e. page articles), news articles, events etc. is represented by so called "content elements". You do not need to enable anything in order to be able to create and edit content elements (assuming you have an administrator account - because editing can be restricted for non-admins, depending on the settings). See the manual to get an overview over content elements in general and which content element types are available by default.
Btw. you need to make sure that the "Articles" module is enabled for at least one section of your layout in your page layout's settings, in order to be able to create page articles and edit their content.
See also the Create the first start page article in the manual.