I once was like most of your colleagues. I am an software engineer and I worked in startups for couple of years. In the end I worked my ass off for nothing. But I guess I can only blame myself. The problem was that I didn't have a clear vision of where I wanted to be in the future.
I think that this guy does not really understand how the web works. I mean, emulating desktop on the web has been tried many times and failed each time. He's right about some things (like people considering 49KB to be a lot) though.
I've tried with Ember.js couple of times and really wanted it to work, but I gave up each time. I don't see how they hope to get more users with this kind of documentation. Documentation and community are crucial for success and adoption of open source software.