As a C# developer I've learned the basics of Rust/Elixir/Go and found that while they're all nice languages, my knowledge of the .NET platform is so deep that for kind of applications I develop (APIs mostly), the tradeoffs of using something new isn't worth it. I haven't come across a problem I couldn't solve with C#. I don't work at Google/FB/Apple, so I don't really deal with scalability issues. F# is interesting, but honestly it's so poorly supported by MS and the community that unless you work at Jet.com it's not worth it.

Don't get me wrong, I love learning new languages/tools, but the cost of learning them deeply is a price that's hard to pay for when you have to get things done at an ever-increasing pace.