Composer: Dependency "drupal/core" is also a root requirement, but is not explicitly whitelisted. Ignoring
Composer remove removes the selected package and its dependancies. However there are, some dependencies like drupal/core that shouldn't be removed. For example, if we try to remove drupal/pathauto this message would pop up, as Drupal/pathauto depends on drupal/path core module, and should/can not remove anything from core or any dependencies shared with other packages. You can see in pathauto.info.yml file what it depends on.