polyfills in general are a really awful user experience.

They are typically pushed by people who use the latest chrome, so they have an excuse not to care about other browsers.

Their preformance, and usability is almost invariably terrible.

You don't need a polyfill to deploy Webp. Chrome automatically sends webp in the Accept headers for images, so on the CDN level you could implement some logic to seamlessly swap in Webp images for the browsers that support it. Imgix does this for instance.