You can easily use Drupal to create the backend for a headless CMS. It's about as simple as turning on the JSON API module that comes out of the box, and then start creating content types.
But then you're having to maintain the CMS, which isn't as appealing as using something like Contentful. It really depends on your use case (like all technologies, of course).
But then you're having to maintain the CMS, which isn't as appealing as using something like Contentful. It really depends on your use case (like all technologies, of course).