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.
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.