Drupal has modernized (its highly modular with OO PHP) and is an excellent enterprise CMS. It can be implemented as the headless backend: https://www.gatsbyjs.com/guides/drupal/
Currently using Drupal 8 with a decoupled Next.js frontend .. works very well. Seem less upgrade to Drupal 9. Advanced CMS editing tools, moderation tools, media management, componentised content modules, content library, all content exposed via JSON:API, multilingual by default .. built on Symfony.
To say it's more complex than WP is true .. but to completely discount it, is foolish.
To say it's more complex than WP is true .. but to completely discount it, is foolish.