With CSS names are global. You have to be careful not to accidentally create a class that conflicts with another one used elsewhere in a different context. You have to worry about whether modifying your class will have downstream effects on elements you weren’t intending to impact. It’s a giant pain. I’ve done it by hand for around 20 years before switching to Tailwind.
Can vanilla CSS be used for a complex app? Yes. But, it takes discipline, and I only have a limited amount of that. I’d rather spend my discipline budget on other things.
That said, nested selectors and CSS variables have gone a long way towards making the vanilla experience much more pleasant. I may have to give it a shot on a side project one of these days.
> With CSS names are global.
Not necessarily. Nested selectors make it pretty easy to apply styles in a modularized way. See https://rstacruz.github.io/rscss/
> With CSS names are global.
In your "programmatic" code (your JS/TS, python, C++, whatever..) your classes are global. Even if the language supports flexible namespaces, or module scoping, you still have to take great care naming because reusing a name will cause you confusion. Giving two things the same name makes them harder to import, and risks clashes and bugs.
No-one complains about this. This is just how you code in all those other languages.
In "programmatic" code, declaring two classes with the same name in the same namespace is generally either some sort of syntax error or one will "shadow" the other; it doesn't just silently merge the behavior of both classes.
Modules make the global thing less of a concern these days.
This is (imo) the most valid argument for Tailwind: the UI semantics of "hero" "card" etc aren't put in CSS, they're put in the module. Modules are typically designed for this encapsulation, and CSS was not.