A website is a collection of pages and links. There are many factors matter when you are creating a website like coding, design, testing, etc. Instead of all of these things, User Experience and UI design is a must.
The success of a website or mobile application depends on a combination of user interface and user experience. Interface designs that focus on the layout of the functionality of the interface are the subnet of user experience design, which focuses on the bigger picture. The whole experience, not just the interface.