CSS supports XML namespaces [0], although I've never seen someone using it.
Shadow DOM supports style isolation [1], although I don't think I've never seen anyone using it outside of toy projects.
There's also a newly proposed containment [2] CSS property, but it's only supported on Chrome.
For simpler websites where you skip using any build tool, I don't think it's a problem. For larger applications that support build tools, css-modules is a good alternative [3].
Shadow DOM supports style isolation [1], although I don't think I've never seen anyone using it outside of toy projects.
There's also a newly proposed containment [2] CSS property, but it's only supported on Chrome.
For simpler websites where you skip using any build tool, I don't think it's a problem. For larger applications that support build tools, css-modules is a good alternative [3].
[0] https://developer.mozilla.org/en-US/docs/Web/CSS/@namespace
[1] https://webkit.org/blog/4096/introducing-shadow-dom-api/
[2] https://developers.google.com/web/updates/2016/06/css-contai...
[3] https://github.com/css-modules/css-modules