The polyfill.js is a popular open source library to support older browsers. 100K+ sites embed it using the cdn.polyfill.io domain. Notable users are JSTOR, Intuit and World Economic Forum. However, in February this year, a Chinese company bought the domain and the Github account. Since then, this domain was caught injecting malware on mobile devices via any site that embeds cdn.polyfill.io. Any complaints were quickly removed (archive here) from the Github repository.
“function” is doing a lot of lifting there. Trackers, ads, and assorted other bullshit is not the kind of functioning anyone needs.
It’s true the average user gets flummoxed quickly when the scripts are blocked, but they can either sink (eat ads and trackers) or swim (learn what scripts to allow). (Spoiler: they almost always sink)