You also have to mess with Javascript on some level, even if you are compiling down from something else.

People who are professional game developers have invested a lot in C++ , have a lot of experience in that area and tend to see Javascript as something for developing websites with.

So on top of the other problems you have persuade them that it's something worth spending the time to get proficient in.

If you're coming from a deep machine and C++ understanding, it's not that JavaScript is tough to become proficient in, but rather, that you of all people have every reason to fully comprehend why it's such an awful implementation choice for this proposed purpose. It's not as if the PC or mobile game market is suffering for lack of cross-platform browser-based compatibility, so why switch to a suboptimal tool?

Do you still have to deal with all of the DOM stuff in html5/javascript?

Yes and no. It's all still there of course. I imagine though if you want to build a game you don't use DOM elements for sprites etc. You just create a giant <canvas> element that you draw to as you would draw to a frame buffer in DirectX etc. You could use DOM elements for the UI though I guess.

Yep. If you examine the source of this game that's exactly how they handle the game itself.