Seriously? Your two examples make the counterpoint to your argument.

The first example in Python would be some variant of

   @get('/')
   def whatever():
       return "Hello World!"

Or in Ruby:

    get "/" do
        "Hello World!"
    end

Or in Go:

    http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
        fmt.Fprint(w, "Hello World!")
    })

These other languages, all popular on HN, are nearly identical to the C#, or even longer in a couple of cases. You'd have to go with a project-specific macro package on a Lisp to get much terser.

The second C# is also quite terse, IMHO. What would you have preferred? The equivalent Python would be something like

    __all__ = ['SampleModule']
    class SampleModule(nancy.NancyModule):
        pass

which, even if you want to say well, no one in real life uses __all__ (which isn't correct) is still nearly the same length. I don't quite remember the Ruby off the top of my head, but it, too, is similar, as would be Perl.

Older C# versions could be verbose, but this seems quite terse to me.