When talking about this phrase, it is strongly related to the concept of minimalism.
A design is much appreciated when it is applied from the phrase, less is more. I personally think that the phrase also leads to modernity in a design. Especially when something is designed with minimalism and simplicity to it.
A few examples of Less is More,More is Less designs:
A kitchen design - So simple yet looks very exclusive
Furniture design with a minimalist touch.