I believe this is also true for development tooling, not just actual code executing in the user's browser. There's no real reason why tools like webpack, eslint

I believe this is also true for development tooling, not just actual code executing in the user's browser. There's no real reason why tools like webpack, eslint, and so on need to be written in JS for most use cases. Members of the Rust community in particular are actively working in this space, building ES parsers, transpilers, and module bundlers. There's no all-in-one solution but even now with a little effort you could replace webpack with Rust-made tools, so long as you don't mind losing hot reloading or code splitting.