Simple design is not a negative term. Actually anyone that can convey a message in the minimal way has got a good design. Design is a strong way to communicate. To be effective in this you would need to take into consideration usability, information and design and try to find the right balance between them. In the end a designer would be able to create a simple clean layout.
To much white space makes the website look unfinished. To little makes it look untidy, overcrowded with information. Use white space to your full advantage. White space increases legibility and can also help draw the viewers eye to a specific section. By using white space you can control the flow of the layout thus helping create an awesome design.
Just a few details can make a website. You never have to complicate a layout with to much information or images. Find small details to make your website stand out. Take for example a heading can be a stand out feature or even Just a snippet with a different font. Just think of something that will be unique to the website that will help enhance your design.
Now I am not saying go all out and create a multi-coloured website. The whole idea of using a bold colour is to make text or information stand out. But this colour can be included in the design creating a nice balance with white space and giving the website the aesthetics it needs to draw the reader in.
In the end its up to a designer or the website owner to decide on what sort of design they want. Everyone has different opinions as to what is appealing to them. We as a designer can only guide them but the final decision is the client. Just remember that a simple design can create a beautiful website.