I've been lucky enough to join a company that is largely agnostic. The devs here seem to be mostly Ruby and JavaScript, but a bit of Python too. I've not done much dev yet outside of a few bug fixes, but simply being out of my element has helped considerably.

My only gripe with C# and .NET is that it's tied to Windows, a fact that immediately locks you down to a single tech stack. Sure, you could write any mainstream language on Windows, but no one does because the language and frameworks aren't optimised for Windows. You're writing code as good as what's written by others on the Linux stack, and your development environment is largely as good as what everyone else is using, but you feel isolated.

For me, it's this perception that leads people to think less of .NET at a platform. You're the guy that drove a Ford to a Volkswagen convention, and even though your car is as good (and in some ways better) than what everyone else has, you'll still feel like an imposter.

In terms of getting over that feeling, I don't think any particular language will help you get over it. My knowledge of JavaScript is alright, so I'm picking up Node/Express at the moment. For the past few months I've been working through Django too, so my ultimate aim is to be in a position where I no longer feel limited by a different language or platform.