Bit of a tangent, but perhaps the issue with separation of concerns isn't so much that it's a bad idea, it's that it's not always a good idea; and secondly that

Bit of a tangent, but perhaps the issue with separation of concerns isn't so much that it's a bad idea, it's that it's not always a good idea; and secondly that css doesn't really enable separation of concerns like that. It's a fine idea to be able to give (essentially) a style a meaningful name, but only if you know what the meaning is and probably only if you intend to use it several times. Since CSS cannot really create complex styles from scratch meaning that you need wrappers and separators and whatnot as purely style elements, true encapsulation that's easy to use without knowing the implementation isn't really feasible. Hence "separation of concerns" - to the extent that it's a good idea in the first place - doesn't work for html+css, and similar concerns mean it doesn't work very well for html+scripts. Put another way, leaky abstractions are worse than no abstractions. Better to keep things transparent and merely expose helpers, instead of pretending you can hide complexity when you cannot really hide it.