To those are newbie to GPO (Group Policy Objects) or Group policy management, your mentor sure told you to not configure default domain policy and instead they will tell you to create a new GPO.
Here is something you should know, “Not all policy settings are workable under newly create GPO”. This means that there are still dependencies with Default GPOs. Even you’ve try to enable “Enforce” or “Block Inheritance”, the Default GPO will always there running. Thus, always research and understand in-dept of GPO.
Below is the supporting article is the answer to you.