It's not about trendiness. It's about valuing experience with a specific stack out of all proportion to what that's worth - perhaps because it's one of the few things that's easy to measure.
I've looked at going in the other direction - onto .NET. There's a lot to like about the framework. But I can take a job on the JVM and be paid like the dev with 7 years' experience that I am, or I can take a job doing .NET and get paid like a fresh grad, despite the two systems being about as similar as it gets.
And I've watched plenty of people in suits be hired at trendy startups. Maybe the bar will be a little hire, but it's not an instant firing the way wearing a t-shirt to many companies would be. A lot of tech companies really are better at this kind of thing than other companies; there is always room for improvement but there's also room to celebrate the things we do get right. Stop listening to DHH.
I interviewed at Loopt (sama's YC company) 4½ years ago. When I went out to lunch with their tech guys, they joked about a guy who had come in before me in a suit, and how that really hurt his chances to get the job. Though I knew enough to dress casually, I was coming from a company in the midwest where I had to wear a suit every day. Both extremes seemed absurd to me.
I eventually turned them down in favour of another offer.
I've looked at going in the other direction - onto .NET. There's a lot to like about the framework. But I can take a job on the JVM and be paid like the dev with 7 years' experience that I am, or I can take a job doing .NET and get paid like a fresh grad, despite the two systems being about as similar as it gets.
And I've watched plenty of people in suits be hired at trendy startups. Maybe the bar will be a little hire, but it's not an instant firing the way wearing a t-shirt to many companies would be. A lot of tech companies really are better at this kind of thing than other companies; there is always room for improvement but there's also room to celebrate the things we do get right. Stop listening to DHH.