That mirrors my experience too on working in various projects. The automatic polyfilling story is such a good thing in theory, but reality isn't as rosy and much more polyfills than necessary are included.
Thanks for writing your article and sharing! One thing I do on my other libraries is also to polyfill a few heavier things asynchronously instead of making everyone pay the price upfront, so for example I detect if a JSON polyfill is required before asynchronously loading that polyfill. I think the expectation for most things is that the browser will support them by default, and it’s ok if all/any polyfills are loaded separately and asynchronously.