GraphCMS – A GraphQL-based Headless CMS

Parse showed immense promise as a Backend-as-a-Service provider and customizable CMS before it went belly up; luckily, it is now open source. See:

http://parseplatform.org/

https://github.com/relatedcode/ParseAlternatives

Have a look at this: https://github.com/dadi/ which is a suite of services designed for publishing. They have separation between data api / website / admin ui which might be what you're looking for. It's used in production on quite a few large UK publisher websites.

Yes, Directus, but it's built in PHP and mysql.