It's really not. Compiler writers, in your words, "write a whole bunch of machinery" so that the code has the intended semantics. It's not fundamentally that different to generating LLVM IR.
I never said every single language compiles via C. Sure, you're right, Zig and Rust generate LLVM IR instead (edit: iirc Zig is moving to their own backend, but I don't think that's relevant), and there isn't much reason not to target LLVM these days, unless you want to target niche platforms that LLVM doesn't support.
> It would be an undoubted improvement to be able to bypass that layer when it isn't useful, regardless of one's opinion on JS.
I will ask you clearly: you are asking for a lot of work from browser makers. What use cases, concretely, will that work actually enable?
If you hate the baggage of JS -- which is fair enough, there's a big mismatch between it and many other languages -- Wasm can be used for most of the heavy lifting, and it lacks that baggage. The JS only needs to be a little layer between Wasm and the browser.
But what will getting rid of that layer enable? What will it let people do that couldn't be done before?
I'm not trying to be mean, so I'm sorry if it came off that way.