Simplicity is not removing things from the screen; it is the discipline of making the right thing visible at the right moment.
Simplicity is not the same as emptiness
An interface that looks spacious is not automatically easy to use. When visual simplicity is not supported by behavioural clarity, it becomes an aesthetic shell. Good products do not expect users to learn how the system works; the system moves closer to the user's mental model.
Reducing the cost of decisions
Every extra option, label and action creates a small decision for the user. As these decisions accumulate, the experience becomes tiring. Product teams should not remove options at random, but build hierarchy around context. The primary action should be clear, secondary actions accessible and exceptions controlled.
Simplicity is a team culture
A simple product is not the work of a design team alone. Product strategy, content, technology and operations must align around the same goal of clarity. Technical debt, ambiguous goals and unowned content eventually surface as clutter in the interface.