> Sites should not be enabling draft specifications
Nice in theory, but in reality sites shouldn't be using features that aren't available cross browser.
:is() is from the same draft spec as :has() but has been available in all the major browsers since 2021 (and shipping in Safari and Firefox in 2020, before it was available in Chrome).
Under your suggestion, :is() shouldn't be used by anyone for another couple of years from now, waiting for unrelated issues in the CSS Selectors 4 spec to be resolved so it can be moved to a candidate recommendation.
No, I wouldn't use it for anything critical either. But then, I'm required to support IE11 as long as Microsoft maintains it.
My attitude towards stuff like this is if you're just using it for a bit of visual extra that doesn't break basic functionality, go for it. Comment above was suggesting site was broken without it. That's just a bad idea. We've managed for decades without this, there's no design that requires adding works in progress, even if it only breaks for 1% of your users.
And if something is a spec in progress, definitely be prepared to keep an eye on it for sudden fixes in the future. It's happened more than once.
