Nonsense. Do you read and write your email using the command line? I use Mutt and Vim for that, and that’s not the command line. GUI with power-user support is just as efficient as Mutt and Vim. Did you use curl to read this thread and submit your comment? I use Firefox with Vimium C, which allows most web pages to be navigated and operated efficiently by keyboard.
Wait, mail clients other than mutt exist?