Startups should look into asp.net if they are not already set on something.
A lot has been going on with ASP.net. ASP.net Core 2.0 was just released. ASP.net Core works on both Windows and Linux so the argument that .net is just a Windows tech is starting to fade. VSCode is a nice text editor with some good extensions. It works on MacOS and Linux as well.
C# is one of the most popular programming languages. With C# you can build desktop apps (WPF, UWP), mobile apps (UWP, Xamarin), programs for IoT, web apps (ASP.net, WebAPI). Not every language has that benefit.
Forget being tied to Windows. Forget the old classic ASP (.asp pages). Forget the old WebForms pages (.aspx pages). ASP.net has been rebuilt into a modern framework.