Imagine that instead of what you do with gRPC/C#, you had to edit proto files just like using Notepad (so is the COM IDL editing experience in VS), and instead of having VS take care of the C# code generation, you either call the MIDL CLI compiler yourself, or manually integrate it on some build step, only to open the folder of generated code, and then manually merge it with your existing code inside of Visual Studio.

That is the gold experience for doing COM in C++, doing COM in C# is somehow better, but still you won't get rid of dealing with IDL files, specially now that TLB support is no longer available for .NET Core.

Quite tragic for such key technology, meanwhile C++ Builder offers a much more developer friendly experience.