In all seriousness, I think his points are valid and well-articulated. This just comes across as a tech demo and nothing more. I can't imagine what advantage re-creating Minecraft in HTML5 would have in and of itself. There's just... nothing new here.
Even if Skycraft were just a Minecraft clone there would be a ton of cool things you could do because it's WebGL: Giving your friends a link they can click to join or spectate your world. Embed your world in your blog. Crossplatform... But Skycraft won't be just a Minecraft clone. Hopefully I'll get to show you that later this summer! :)
Right, it's a "social game" that encourages intelligent gameplay. Building it as an open platform that others could add logic (say in asm.js modules) would be a cool hook. I'm encouraged by what Minecraft is doing in making a very nerdy game cool, and supplanting mind-numbing entertainment or purely violent games for younger kids. Having something like Minecraft but instantly accessible though the web could be a good way to bring new players into the genre, even if they end up being Minecraft players at some point.
Sure about that?