Yes, their C++ LSP isn't really good and I've heard C# isn't good either - but that's because they want to sell Visual Studio too. But especially "Remote SSH" and "Dev Containers" are so called game changers. And their Typescript and Python extensions are actually good.
C# extension works well and uses Roslyn Language Server that is part[0] of the Roslyn (C# compiler) itself - this is what the base C# extension[1] uses. Both of these are licensed under MIT.
The closed-source part is 'vsdbg' which is Visual Studio's debugger shipped as a component that the extension uses. It, however, can be replaced with Samsung's 'NetCoreDbg' by using the extension fork[2].
[2]: https://github.com/muhammadsammy/free-vscode-csharp (please consider giving it a star, it's the only actively maintained alternative and other tools end up relying on it downstream to support debugging - VSCodium as well as Emacs and Neovim with VSC extension bridges)
Lately they've begun embedding the same C# analysis stuff they have in VS into VSCode if you pay for the license. I haven't used it in anger (long since left for Rider), but it has come in handy when troubleshooting people's VS issues at work from my Mac. The test explorer now blows up in exactly the same way in VS and VSCode :)
