But it's a performance killer

https://dev.to/srmagura/why-were-breaking-up-wiht-css-in-js-...

Edit:

See also this thread on Bluesky

https://bsky.app/profile/infrequently.org/post/3lnehf53bpcl7

It can be, depending on how it's used. But most of the modern tools I've seen are specifically designed to compile away the dynamic aspects of CSS-in-JS, meaning it essentially becomes a different way of writing normal CSS.