I´ve recently been in charge of hiring a lot of people and have probably done +100 interviews in the last year. I generally don´t mind the stack/language candidates have been using but I always value very highly that they have used different stacks and languages during their whole carrer. When I interview 5+ years .NET developers who haven't used another language, not even in their spare time, the result is usually a…
It's all about using the right tool for the job, and if you only have a hammer, you start treating everything as a nail.
I've used Java, .NET, PHP, Node, Ruby, Python and more in my career - each one for different uses and where there was a good fit.