Design systems become slow when every visual decision requires a new abstraction. Modern CSS already provides the primitives for responsive type, fluid grids, theme variables, and component-level adaptation.
Start with constraints
Define spacing, type, color, radius, and motion as a compact vocabulary. Components should compose those constraints rather than introduce a private visual language.
Keep the escape hatch
A design system succeeds when ordinary work is predictable and unusual work remains possible. Native CSS is a durable escape hatch because it stays close to the platform.