It does have an integrated debugger, build systems, code intelligence, refactoring tools, and version control.

What other things need to be integrated before it can be blessed as an IDE?

This is what I'm saying! At the risk of ad hominum - I feel like a lot of the comments classifying VSCode as merely a text editor haven't really used it for development - at least not directly or in a long time.

Though this whole thread could really be considered off-topic since the original post is about Visual Studio for Mac!

Does it or are they available as a plugin?

Yes. These features are directly supported by VSCode. They aren't added via plugins.

Support for specific languages/debuggers/build systems is provided by extensions.

Look up how LSP and DAP work for example. A hugely successful extensible IDE system.