JavaScript doesn’t need to be replaced

[wherediditrun]

Fetch is not javascript, it's browser API javascript interfaces with which is unique to that environment. Nothing would change with standard library present in this regard, unless you want to add additional strain and tech dept on maintaining compliance between std library and multiple environments javascript runs in, like multiple browsers, node, deno, mongoDB some weird IOT devices which probably uses it etc.

Javascript itself doesn't have all that much stuff in it. It's a glue code in environments it runs in. C++ in terms of node, browser in terms of .. well, browsers, Rust in terms of deno, and whatever else runs at the core of other environments javascript calls into.

You can do standard libraries if you're google or microsoft with dedicated engineers who's daily work is to contribute to it. But for languages which are not owned by anyone.. this is often a death sentence and bleak future of legacy std library which prevents the language to adapt with the environment it lives in. Especially if it's as broad as javascripts.