Iteration does not guarantee good design but lack of iteration most definitely results in bad design.

Onur Cobanli explanat:
You must most definitely try different variants of your design, especially if it is a product, interface, service or experience that will affect millions. It is always better to try to improve your design, you must iterate, you must think always, how you can make it better; even if you have great design, iteration could lead to a superior design. Iteration is one major way a design can be made better; designs can be improved by many means, such as having better observations, having better control and access to knowledge and materials, and being in a better mood when designing, so these all help, but as you realize, these are mostly external; i.e. you may not have access to better materials, you may not have opportunity to make more observations, but you will most likely have control over your subjective time; iteration is more an internal thing than external, it is something you can definitely control; you should iterate as much as it is economically feasible to do so, with everything else constant, the iteration will help you make better, superior designs.