If you're happy to sacrifice the benefits of .net and spend time writing basic Win32 apps, that's totally a choice you can make. Or even just use .net framework 4.6 and not add any extra dependencies.
I'm not really sure what you're complaining about here. .net core is split into tiny packages - if that is hard to handle in your very special environment, you get to use special solutions to make it work.
That's besides the point I was making, which is that there's runtimes/languages which lean towards "internet required for development" or even "internet required for building" while there are also languages/runtimes which are self-contained and independent.
That being said, WinForms is also "just" a Win32 wrapper, I don't see a compelling reason why a similar wrapper wouldn't be possible in pretty much any language. .NET 4.6 is a fine choice too, especially because you're not forced to ship runtime and standard library, as Windows already has both.
I believe that's very much related. The more of the nice wrappers you provide, the more you have to decide if someone needs them all or are you providing them on demand. With .net core doing more splitting than framework and with Java going through a decade of jigsaw, I think we collectively decided we don't want to include everything upfront.
We don't even require the internet for building/development. In .net land you require internet to get the dependency you're using the first time. If you want to get them all and distribute/install before you start development, you can totally do that. It's just not the default behaviour.
I'm not really sure what you're complaining about here. .net core is split into tiny packages - if that is hard to handle in your very special environment, you get to use special solutions to make it work.