It's probably a tiny fraction of the C#/dotnet ecosystem. But hobbyist meme creators mostly care about games, I guess.

No, as other's have pointed out it's not. There are plenty of other areas to use it, even in other game engines. OP is just trying to make it seem funny by making the exaggerated narrative that it's the only use case for C#. If Boo was still around in Unity this joke would been accurate with that, don't think that was used anywhere else

It is also the language of DotNet framework so hardly.

No, C# is a general purpose language that Unity has a botched, outdated version of.

Not at all. Unity's use of C# is pretty unconventional even. Not representative at all.

Absolutely not. It’s used everywhere on the web and other places.