If you've really used .NET "from beta", you'll know that the platform became a snoozefest around 4.5, only to be revived around Core 3.0. "Insanely rapid platform churn" it is not.
And abandonware? Silverlight, sure, not much future in that (although it still runs fine on its own) but how is Adobe Flash doing these days, talking about "other platforms".
Or Java Servlets? In-browser applets?
I've had to migrate my server-side Java code at least twice in the last decade. But possibly I'm just not understanding the needful?
In fact there was a hell of a lot of churn while Microsoft pissed around with the MVC middleware stack implementation and throwing async in which has been buggy as hell on classic. And of course there was the entire “we decided to gut WCF and WWF and AppFabric” thing.
I lost count of the hours I spent digging through deadlocks and spinwaits.
On .net core there have been many many breaking API changes over just the last three years which have broken everything from libraries to the stack. There has also been absolutely zero to no guidance on what best practices are in the current hour. All the documentation and articles out there are obsolete within a gnat’s fart of time after they are written.
There was a lot of change and not a lot of thinking that went into the platform over the years. This costs big money for clients.
Your complaints about the "MVC middleware stack implementation" only underscore the fact that you're making unsourced allegations here. DotNET middleware has been remarkably stable, only requiring some minor adjustments to source code.
So, really, can you give me one, just one concrete example of how .NET has "costs big money for clients"?
Software maintenance costs money, yeah. In Java, in Golang, in (dare I say it?) Rust, in C#. But is the latter platform really that much worse than any of the former?