Debugging mode is not the same as root permissions on your device. With debugging mode you are logged in (shell) as user_shell and with root you are user_root. The user_shell doesn't have the permissions to read the app specific directories in /data/data/PACKAGES to do a backup of all your apps. Only user_root, user_system and apps themselves (only for own directory, but others not) can access these directories r/w and read all the data within.
Exception: An ADB backup is able to backup app data of those apps, that are included in the Google Backup ('device settings > System > Backup' or open settings > searchbar > 'backup').
For a detailed overview visit: drive.google.com/drive/backups