C# is a pleasure to work with. It's got generics and good support for asynchronous I/O. .NET Core is also very good, it's dead simple to spin up an API serving backend using .NET MVC.
Lastly, I think the community is great. I have jumped into a couple different projects - one is a MySQL driver and another is a MySQL implementation of the EntityFramework ORM. I was able to contribute after just a few weeks of working with C#. Microsoft seems very dedicated to continually improving the language as they develop in the open on GitHub and take user feedback.