While I think most people will agree it's not a dead end tech stack and their will be companies hiring for decades to come there's a element of truth here that isn't being discussed.
From what I can see Microsoft stack is used mostly by enterprises that are not engineering centric.
For all of the largest engineering centric companies that pay top of market only one heavily uses Microsoft....and that is Microsoft. Furthermore most VC funded startups also tend to shy away from Microsoft stacks. (Exception being parts of Azure compatible outside of the MSFT stack and other polyglot tools like VScode)
So while I don't think you need to worry about employability I wouldn't recommend investment in the stack to new graduates. Obviously my perspective is limited so I'm curious to hear counter points.