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.