I'm all for building from scratch a lean minimal runtime platform as you describe (that's what operating systems should be), also it should be "easy", take a minimal Linux kernel and add some thin APIs on top. But good luck turning this into a project that gains any traction.
Using the browser platform to bootstrap such a thing isn't such a bad idea in comparison... sooner than later we need to depreciate the ugly parts, like WebRTC, WebAudio and trim some fat here and there, but other platforms have their ugly parts as well (look at the mess that is Android).
Using the browser platform to bootstrap such a thing isn't such a bad idea in comparison... sooner than later we need to depreciate the ugly parts, like WebRTC, WebAudio and trim some fat here and there, but other platforms have their ugly parts as well (look at the mess that is Android).