The fastest way to ship a new feature is to build it in isolation and skip the shared design system "just this once." Do that enough times and the product quietly stops feeling like one thing, one screen at a time.
We maintain a small, strict component library — spacing scale, type scale, motion curves, button and form states — so new features are assembled from existing parts by default, and a one-off only happens when there is a real reason for it.
This is what actually makes fast shipping sustainable: the constraint is not a slowdown, it is what prevents next quarter's roadmap from turning into a redesign to clean up this quarter's shortcuts.