I think one major issue with this is that ES basically can't break backwards compability, ever. Observables are a good example, actually. If we look at RxJS, wh

I think one major issue with this is that ES basically can't break backwards compability, ever. Observables are a good example, actually. If we look at RxJS, which is sort of the inspiration behind observables I guess, we'll see that they are now at 6th major version of the library. Migration from 4th to 5th made bunch of renamings and other breaking changes, which just wouldn't work in ES. Migration to 6th includes an additional compability layer, which again would be permanent piece of bloat if it was in ES standard. And all this while some other HNers are saying that the browsers are too complicated and its so sad that there won't ever be completely new independent browsers... :)