I don't think it is overlooked. JavaScript doesn't scale, both in terms of code complexity (callback hell) and across cores, and the "gold standard" these days

I don't think it is overlooked. JavaScript doesn't scale, both in terms of code complexity (callback hell) and across cores, and the "gold standard" these days is microservices, which has a ton of issues. If you want to look at bolt-on async working, check out C# or Rust. They've basically taken JavaScript's new async/await and added threading (at least Rust has, not sure about C#). You can write an async app and have it run in a thread pool without much fuss. I don't know what the story is for Java, but seeing as C# is effectively the same thing, it's not hard to imagine adding async being easier than adding threads or performance to JavaScript.