My basic definition of UX is providing users data and decisions in a certain context.

In some contexts (selling), certain things are more important, like having a beautiful appearance and no data overload. Your first time user may be your most common user, because they may only make one purchase per [lifetime, year, etc]

In other contexts, for instance industrial controls, data density is more important, and the user may be expected to take more time to learn the interface. There is still some need to accommodate new users, because everyone is a new user at some point.

In any case, there is a decision to be made, aided by some data presentation.