CGI basically is a protocol between the webserver and some process. It didn't go out of fashion because of C (many/most CGI scripting for a time was perl and php or even bash), it went out of fashion because people wanted (or were told that smart people did this) to use languages that had runtimes which were expensive to run in a fork()+exec() execution model like Java.

You can use it with any language that can read stdin and write stdout. Yes, printing and reading.