Mostly agree with the above, outside some ES3-ish scripting environments (Adobe and others), polyfills for a lot of functionality isn't needed strictly for JS support. And even then, can still be part of bundling or shimmed outside your application script(s).
And if you're bundling, then you can add them into the process. I've been avoiding most things that could require a polyfill since 2018 or so anyway as green browsers are pretty feature complete. As much as I'd like the F# style pipelines, and there are a couple other niceties, I don't miss much.
Polyfills are often necessary because new features are still added to the standard library, and runtimes all have varying levels of support for new features.
