The @apply rule and custom property sets most likely won't get any more support from browser vendors as the spec is yet considered deprecated and alternative solutions are being discussed.
大意就是@apply规则和自定义属性集还没有得到浏览器厂商的更多支持，因为规范仍然被认为是不受欢迎的，并且正在讨论其他解决方案。
目前还在继续学习cssnext中！