For a typed language completion like Intellisense is a very important tool for any developer. There is limited completion support available in VS Code. If you want a proper IDE for .NET on Linux, try out JetBrains Rider. It is not free, but great.
I don't understand what you dislike about the API documentation Microsoft provides with .NET, it's not always perfect, but I would say it has nearly 100% coverage: https://docs.microsoft.com/en-us/dotnet/api/
And because .NET used to be Windows only there are a lot of Windows tutorials. But you can anyway skip them, as they mostly describe the old .NET 4.x. Find newer .NET Core tutorials. Even if they provide you screenshots of Visual Studio on Windows, you can do all of it with any text editor. Some scaffolding you maybe need to do on the command line.
You exactly understand and confirm my point - outside of the bubble Windows/VS bubble, it's not a super nice developer experience. If you want to work hard to make it work: you can, but... why go out of your way?
And I haven't said anything about building GUIs here yet, which is another world of pain on .NET.
I don't understand what you dislike about the API documentation Microsoft provides with .NET, it's not always perfect, but I would say it has nearly 100% coverage: https://docs.microsoft.com/en-us/dotnet/api/
And because .NET used to be Windows only there are a lot of Windows tutorials. But you can anyway skip them, as they mostly describe the old .NET 4.x. Find newer .NET Core tutorials. Even if they provide you screenshots of Visual Studio on Windows, you can do all of it with any text editor. Some scaffolding you maybe need to do on the command line.