CSS-in-JS: The Great Betrayal of Frontend Sanity

CSS-in-JS was marketed as a solution to global namespace issues and styling complexity, but it introduced runtime performance penalties, debugging nightmares, and hydration bugs. The author argues that dynamic CSS generation tied to JavaScript execution creates measurable overhead and developer friction. Modern CSS features like variables and container queries now handle modularity natively without runtime costs, making CSS-in-JS an unnecessary abstraction.