No one wants a CLI in Ruby, and if you look arround there is no popular CLI written in Ruby it's one of the worse language to write CLI in because no one has the Ruby runtime installed on their machine, then you have different architectures, different OS etc ... Go is way way better than Ruby on that topic.

As for complex data structure, I don't understand exactly what do you mean, as if a dynamic language would model that easier than a strongly typed language.

When you get a single binary for CLI it's hard to use anything else, the pain of using pip for anything python based.