Large portals accumulate CSS debt. New features slow down as styles conflict.
The solution stack
Design tokens (color, spacing, typography) in one source of truth.
CSS custom properties for runtime theming (light/dark/brand).
Subgrid to align complex components with parent layouts.
Cascade layers to prevent overrides warfare.
Governance
Ship a component library, document usage, and lint style rules in CI.
Outcome
Fewer regressions, consistent UI, faster delivery.