In the old model, you had semantic markup (ideally) and css on top, that you could swap. He says: " in modern web apps we don’t only render content in simple s

In the old model, you had semantic markup (ideally) and css on top, that you could swap. He says: " in modern web apps we don’t only render content in simple single-element containers like boxes and circles, but in drawers, modals, floating panels and other complex, multi-element components. [...] All web frameworks have a good abstraction for this, of course: components. [...]" Now, I've always missed a way to apply style on top of complex components. You can still use CSS, but as he says there is a mismatch when you change the internal HTML structure. It would be great if you could use React components like <Dialog> <Button> </Dialog> and then specify separately in a theme component the styling - not just CSS, but also what elements to use to build it up. Of course, you can just use separate components for each theme - ModernButton, DarkButton, RetroButton. But there is a lot of room for errors and the interfaces can diverge. Better to have one opaque Button component that gets passed the Style from somewhere else. I actually started working on something like this - a Electron based Desktop Widgets tool, where you could write components in React and switch themes. But since I'm a React novice I could not find an architecture that I was happy with (and the idea of using an Electron instance to decorate my desktop to monitor performance seemed a bit crazy :-)).