I disagree, HTML/CSS have come a long ways in the past few years, in terms of browser compatibility and features. I don't see how introducing a new layout engine would help. That's just another standard that every platform has to support. Using WebGL would be great, but so far WebGL support on mobile is not great.

If you haven't worked with web tools recently you should see how far they've come. With JS frameworks like Angular or Ember, and crazy fast build tools like Gulp, it's pretty nice developing for the web these days