It's distinctly possible that Unity3D will "rescue" this aspect if C#, although from what I saw of the community it's not there yet. Probably the lack of a good package / dependency manager - oh, and the lack of up-to-date C# support (last I checked you were stuck way back with 3.5).

Yadda yadda, if I wanted to "fix" the lack of an open source community in C#, I'd start with the Unity3D community.

In the latest Unity version (2018) you have access to C# 6 (stable) and .NET 4.6.

The problem with that is, there are now open source game engines coming on the scene that are promising (in the long run, and yes it's a BIG maybe) to upset Unity's stranglehold, that support Python and in the future C# to lure away Unity devs. I'm speaking of Godot. I'm not sure how successful they'll truly be but I, for one, am hoping they bring a solid rivalry.

Python as a scripting language makes sense, in this arena, anyways, as it's the scripting language for Blender. A single scripting language for 3D software and game engine in a game studio just makes sense.

Only makes sense in modern game engines if it comes with a JIT.

I can go for a coffee when Blender does some kind of data transformation, I can't do that in a middle of a rendering a frame 60 times per second.

It can also do .net standard 2.0, which is great for library compatibility, and the experimental (but working) incremental compiler is Roslyn based and can do c# 7.2.

Oh, horray! I stopped working with Unity3D, and so haven't been in the loop

I don't think that's accurate, we use opensource .net dev stack since 5/8 years, and since 3 it can be deployed on win, linux and osx.