If you think WebAssembly (or asm.js) is a good idea, I would very much like you to do the thought experiment of what design decisions something like WebAssembly would have made 15 or 25 years ago, and what consequences those would have today.
Helpful research keywords: Itanium RISC Alpha WAP Power EPIC Java ARM Pentium4 X.25
I can't think of any software development API that ended up being perfect 15 or 25 years later. Javascript certainly isn't. Java applets, ActiveX controls and Flash very much weren't, but, at the time, they did things you couldn't with the standard web stack.
And we're better off for learning the lessons of the failures, creating improved technologies to replace them (HTML5, JIT Javascript engines, etc), and building on the successes to continuously do more things that previously couldn't be done in the browser.
Will WebAssembly be perfect? Of course not. Will there be unanticipated problems? Of course. I would not at all be surprised if it becomes the next Flash. But it's better to move forward and keep innovating with new web technologies instead of letting the platform stagnate.
We've tried feature-freezing the web for a few years; it was called "Internet Explorer 6" and it sucked.
Helpful research keywords: Itanium RISC Alpha WAP Power EPIC Java ARM Pentium4 X.25