A brief is not a wish list
"Make it look modern and professional" is a preference, not a brief — it gives a designer no way to know what a successful result actually looks like, or when to stop revising. A useful brief describes the situation and the goal, and leaves the visual solution to the designer.
What a working brief actually contains
What the deliverable needs to do (not just look like), who it's for, any hard constraints (existing brand colors, a required deadline, a specific size or platform), and — critically — one or two real reference examples that show the general tone being aimed for.
Why vague briefs cost more, not less
Skipping a proper brief to "save time" almost always costs more time later, spent in open-ended revision rounds trying to reverse-engineer what "better" means after the fact. A clear brief up front is usually the single fastest way to get to an approved result.
A brief doesn't need to be long
Five direct sentences that cover the goal, the audience, the constraints, and one reference point will consistently outperform a long, vague paragraph about wanting something "unique and eye-catching."