I think it is a bit early to declare .NET dead as a technology... It is still by far one of the best pieces of software developed by Microsoft and has adapted for years and is increasingly adapting to this more open world.
But certainly looking at the big picture it would seem like JavaScript has taken over the world, and is infiltrating the last bastion of .NET and Java, the large corporations.
And that's a good insight. Just like I stated in the article "Believe me, you don't "just rewrite" 4 decades of COBOL; the same holds true for the .NET stack." However, when Fortune 500 companies are moving to it; the writing is on the wall.
I think your piece is very much on point although I only read 50% so far I will finish it and go through the code as well. It is well written and your arguments are solid.
The only thing is I disagree on one thing for server side code I think .NET will evolve and adapt.
On the client the war is over JavaScript has won, and its given us what .NET and Java promised all those years ago; true cross platform UI/client apps.
Yes, I could see many organization adopting only the Mongo and Angular portions of this stack and leaving their API to leverage the .NET Web API; it too is RESTful.
I think they did so many things right with Web Api 2.0 and SignalR. I think there is the possibility in the future where you can take only the parts of the framework you want, maybe ASP.NET vNext.
Again in a lot of ways though those are a response to Node.js and socket.io
All of your points stand: how expensive it is, the fact that it is a bit heavy, and not homogeneous.
I still think it will evolve and will not fall behind like Java etc. but it does not hurt to hedge a bit and start learning the "MEAN" stack :-)
But certainly looking at the big picture it would seem like JavaScript has taken over the world, and is infiltrating the last bastion of .NET and Java, the large corporations.