Copywriters need to understand and respect art direction.
Account planners have to be creative and recognize great work.
Creatives have to be able to write their own briefs and recognize great insights.
AEs should understand and respect great creative.
Planners and creatives should understand and respect client relations.
Clients should understand and respect great creative.
Agencies should understand and respect the client’s needs.
(Notice how it gets more and more difficult?)
You should know something about everything and everything about something. If you want to succeed in this business, start by understanding everything about your craft and almost everything about the crafts of those around you.