JS cannot simply release a standard library and every browser will autoupdate to have it. It takes browsers years to get up to date with the latest in ecmascript. So any solution would look at 5 years before adoption. This is why transpilers have taken over: polyfill and shim all the things. It will still add bloat to js bundles, it will still require npm packages.
This is the world we live in and it is unique to javascript.
The best time to add a decent standard library was 10 years ago. The second best is today.
Shipping a decent set of core libraries would do wonders for package sizes. You could cover a lot of use cases with a relatively small API surface area (the classic 80/20 rule) and you'd find that a lot of duplication in implementing the fundamentals in third party packages would just go away.
Browsers update pretty quickly now, anyway. It's likely that in the future we will see most sites using a lightweight package for modern browsers and a heavy polyfill for IE, which is fine by me.
This is the world we live in and it is unique to javascript.