[petetnt]

I don't really care to comment about the practice itself, but the "Polyfills that don’t polyfill" section is missing the point: the function is called directly instead of patching the global object so that the global object is not polluted by an possibly non-standard implementation. Additionally it does use Object.defineProperty if available - furthermore it doesn't even call itself a polyfill in the first place. If it's needed in 2023 is a valid point however.

[fiddlerwoaroof]

I think it would be better to just expect the standardized functions to be present and then document that the project needs them (e.g. via peer dependencies), allowing users to install them themselves as needed.

[shpx]

That's a lot more work than your library just working in more places.

[fiddlerwoaroof]

I don’t think it’s all that much more: basically every bundler I’ve used uses browserslist to include polyfills for the developer’s target audience.

But, also, I think this sort of easy path inflicts a huge cost on the ecosystem as a whole: writing to the standards and expecting your users to supply a compliant environment solves a lot of N*M problems in the dev process.