Your argument assumes that building good web applications is merely a function of tools. It's not.
We have a performance-per-watt wall, plus a heat wall, plus a weight wall in mobile hardware.
There is a reason that Apple is pushing C-based development without as much as a garbage collector, it's not just the stubbornness of Jobs. It's because a dynamic language with state-of-the-art VMs struggles hard to do basic smooth animations on current-gen mobile hardware, and will continue to struggle, for at least the next five releases of Nitro.
You're going to need something like a battery revolution to build the mobile web app panacea that you want.