As someone who has developed with .NET (using VB, C#, F#) for almost 15 years, I am not sure if I would still advertise .NET as something focused on developer productivity, when in the context of introducing bleeding edge tech. It is a great framework, but I've found much more productivity with Elixir after just 1 year of using it. C# still suffers from statefulness, null references, and boilerplate code, even after newer versions of the language provide some tools to reduce those.
F# is a good alternative to C# if you want to stay in the .NET ecosystem and reap the benefits of functional programming, but I found the compiler to be very slow, 3rd libraries poorly documented, the language excessively complex, and 3rd party IDE support to be limited (as of version 2.0 anyway).
Is developer productivity still a focus of .NET?