"Mostly Windows" is a limited view. Most modern .NET developments end up in a docker/kubernetes Linux container. In the first year of .NET Core some shops did Windows deployments but now, that is long gone.
But I agree. .NET will not replace Java or any other serious language.
> But I agree. .NET will not replace Java or any other serious language.
I think you have to specify a domain to make that statement reasonable.
I think .NET is used more than Go for example. Maybe more than NodeJs also for server systems. Less than Java. If we compare to C++ it is very much down to domains. I don't hear about many enterprises using C++ for server backend code but of course they exist. And so on. .NET (or C#) may already be "leading" against a lot of other languages and then the question is if the others will replace C# or not. And if it will take some of the market from languages like Java which I think it will but not all.
We occasionally use C++, but instead of the holistic approaches that tend to be discussed with everything in language X, we just write a native library that is then safely used from Java/.NET.
Basically what everyone usually advocates as "Python" in performance critical stuff, but we get the the productivity and JIT/AOT tooling from Java/.NET eco-system as well.
SharePoint and Sitecore are .NET Framework only. Only CSOM is Core and Sitecore just released their first Core support last month, and most enterprise projects ends up plugging into them.
Forms, WPF still have issues running on top of core, UWP is stuck on Core 2.1 compatibility and .NET 5 is focused on desktop deployments with UWP future uncertain.
The whole “serious language” thing is ridiculous. You are reading this on a web service originally developed using Paul Graham’s custom made-up dialect of LISP called ARC, which runs on top of Common Lisp.
It’s pretty much as far away from “serious language” as it’s possible to get, but here you are happily using it anyway.
But I agree. .NET will not replace Java or any other serious language.