Efforts like Managed DirectX and XNA were driven by highly motivated individuals, and were quickly killed as soon as those individuals changed role.
One could blame them for leaving the project, or see that without them managemenent did not care enough to keep them going.
While at the same time, since Unity relies on such alternative approaches, it also creates a false perception on how good .NET and C# are in reality, for those devs that never learned C# outside Unity.
In a similar way it is like those devs that have learnt Java in Android, and get sold on the Kotlin vs Java marketing from Google, by taking Android Java as their perception of what it is all about.
Going back to game development and .NET, at least Capcom has the resources to have their own fork of modern .NET, e.g. Devil May Cry for the Playstation was done with it.
"RE:2023 C# 8.0 / .NET Support for Game Code, and the Future"