I used to use Ruby for CLIs. Then I started using Golang and delivering compiled binaries for each OS that I supported. This has been a game changer for me. With the CLIs that I've worked on that are open source https://github.com/RiotGamesMinions/motherbrain and some other ones in Ruby, we consistently had issues with rubygems and having people be able to run our CLI from version to version.
Using something like Golang for distributing compiled binaries means that as long as they have the CLI, it will continue to work. With Ruby, Python, PHP, etc, there is absolutely no guarantee that your application will work in the future.
Go has been a game changer for me also. There is also a very good package https://github.com/spf13/cobra that can make the development of complex CLIs easier.