There is a certain clarity that comes from removing things. Not adding.
Most of the best tools I have used do one thing well. Most of the best interfaces I have seen show only what matters. Simplicity is not about being minimal for the sake of it. It is about respect for the person on the other end.
Less, but better
Dieter Rams said it decades ago. It still holds. Every feature you add is a decision someone else has to make. Every option is a small tax on attention.
In practice
When I start a new project, I try to resist the urge to add things. Start with the core. Ship it. See what is actually missing before reaching for more.
It is harder than it sounds.