Traditional content management systems are monolithic beasts. Just to make your website editable you need to accept the web framework imposed by the system, the templating engine used by the system, and the editing tools used by the system. Want to have a better user interface? Be prepared to rewrite your whole website, and to the pain of having to migrate content between different storage systems. But none of this should be necessary. When web editing tools were more immature, it made sense for the same people to build the whole stack from database content models to web page generation and editing tools. But that was ten years ago, now we could do better.