Well, he also created GCC and GNU Emacs.
Linux and the idea that developer tools should be free wouldn't exist without him.
But that's also the kind of people we need. Companies are not going to compromise on their profits, we need someone to balance that and not compromise on software freedom. With these two extremes we can take an balanced position and that's how we got Linux and distros like Debian: it is free software, but it is also pragmatic. If we only had pure GNU (HURD), we wouldn't get far, but if we didn't have GNU at all, it would be even worse.
Richard Stallman didn't just talk. He actually wrote code, famously Emacs, and started the whole GNU project. I am not aware of recent technical contributions though.