The point is both Adobe and the W3C are guessing. Think how much faster we could advance if it was put in the hands of the community. A community that constantly implements, gets feedback, re-implements, collaborates. You only have to look at three.js (https://github.com/mrdoob/three.js/) and similar to get an idea of what can be built on a low-level API.
[Edit: guessing, not second-guessing]