What is a Graphic Designer / Web Designer?
Suppose for a moment that you've decided to build a house. Now you aren't going to do the actual work yourself because you're going to hire a contractor.
Your contractor will design, construct, and decorate your house for you (it's my fantasy, go with it). When completed, (s)he will give you the keys to your new house.
Now, how would this house building evolve? Would you simply say to the contractor "build me a 2000 sqft house" and leave the contractor to provide all the design elements, the colors, textures and furnishings? No, you wouldn't. While the contractor could provide you with a 2000 sqft house, it's very unlikely that it would meet your wants, needs, or desires.
So you provide the contractor with a guide to how your house should be constructed, what it should contain, and how it interacts with your neighborhood.
Your contractor does all this after signing a contract with you. The contract spells out a role for each person involved in the construction. If you can provide some of the labor, your costs will be lower. If you provide the right input, you are assured that your house will truly be what it is you wanted.
Nobody knows how you want your house to look, feel, and communicate better than you do. Your contractor can make some educated guesses about you and place those assumptions into your house, but will you be really happy with the results? And wouldn't you expect the contractor to charge you more for providing these things instead of you providing them yourself? Time is money, and contractors don't give away their time.
So, what do you do? You provide the contractor with input about how your house should look, feel, react, communicate with others and then your house gets built the way you want it. It says what you want it to say. It's comfortable, and it looks good. You're happy.
Now a little substitution game:
Replace "contractor" with "Web Designer", replace "house" with "web site", replace "design elements", "colors", "textures and furnishings", "info" and "input" with "content". Replace "neighborhood" with "customers". Now go read the story again.
That's what a web designer is. (S)he can build you a web site. The more input you provide, the better able your designer is able to meet your wishes for your site. You provide the building blocks the designer uses. If you want the designer to provide the building blocks, don't complain about the additional cost. Time is money, remember?