The definition of an expert is a person who is very knowledgeable about or has mastery in a particular area.
Here’s another definition of an Information Security Specialist or whatever the Firewall guy is called nowadays.
I was so unprepared for the Division 2 Raid that I had to go back to the drawing board to look at my built from knee pads to backpack to armour and guns. So much for being an expert gamer.