Website design leads an important role in the development of any website. The interface in which the viewer navigates is the finalized piece of a painting; it should be perfect. The goal of design is to bring the audience to the website through the means of an attractable template and an easily navigable structure. As well, the user should be persuaded into returning to the website to do business again in the future.
Ease of use is key; if a visitor is capable of navigating throughout the website easily to reach their destination without hassle, they are more likely to return to do business once again. Even more, they may be likely to share the website with others, increasing traffic as well as revenue (or participation if it's a free, community-based website).
Knowing this, a simplistic design seems to be expected. However, a complex design is certainly applicable, so long as easy navigation is doable. Usability tests can be conducted to discover the ease of navigation: multiple people are asked to navigate to a certain part of the website without prior knowledge on the location. If they succeed without a problem, chances are your website is usable!