What actually moves the needle in a design system

Everyone starts a design system with components: buttons, inputs, cards, the visible layer. That part matters, but it is not what decides whether the system is still in use eighteen months later.

What decides that is governance: who can propose a new variant, how a breaking change gets communicated, and whether teams can pin to a version instead of being forced onto main. Without that, a design system turns into a shared node_modules folder that everyone is quietly afraid to touch.

The other piece worth documenting is the reasoning, not just the API. A component's props tell you how to use it; they do not tell you when not to. The design system that actually saves effort is the one where an engineer can answer "should I use this or build something custom" without having to ask the platform team first.