There's nothing wrong with using a normal programming language like Ruby either. Many people use RoR because it's a good tool, not because it's 'cool' (aside: is RoR even 'cool' these days?). All tools have their strengths and weaknesses and while I tend to agree with you that C# has nicer debugging tools, that is only one of many important considerations when choosing a tool.
Agree with your other points, particularly about doing something that isn't social media.
Too bad the author kind of participates in this as well with hipster terms like 'ex-rockstar', 'bootstrapping' and 'lean startup'.