I think its greatest feature is that you can setup one environment (with a lot of options) and get very good tooling for a wide varity of languages. No need to learn about the ideosyncracies, absent features and novelties of different IDEs.

If I want to try out something different (or familiar) all I need to do is install one extension (and maybe some packages) and for the most common languages I get a debugger, autocomplete, syntax, etc. without needing to look for a language specific IDE which might or might not have the features I want. I can switch between different tasks all without leaving a common, relatively complete environment. Likely any given repo contains different languages, even if it is just markdown having one software which does it all is pretty neat.