Then once you need to go beyond the standard libraries it becomes a nightmare to deal with. In some cases, like extending the AD libraries, it’s sort of easy to extend classes with methods but the documentation on how to do so tends to assume a lot of domain knowledge. In other cases like if EF’s standard functionality isn’t enough for you, or you need to deal with weirdly formatted XML or non standard SOAP requests (don’t ask) it can be such a nightmare that it’s sometimes easier to write a micro-service in another language to do the “translation”.
I think it speaks of a language that doesn’t see too much use by its own creators. I may be wrong on that, but having build a lot of things for Azure, Typescript has often felt more like a first class citizen than C#. Obviously not for everything, far from it, but sometimes and those sometimes are enough to make C# troublesome because unlike things like typescript that are great second class citizens in the Microsoft ecosystem, C# isn’t. It either fits really well or you have to fight it.