Holy mother of God, Slime is ugly. Also, the screenshot is ancient. macOS hasn't had scrollbars like that for ages. This is from the official website.
You can really tell that these Lisp guys don't worry too much about appealing to newcomers.
SBCL, the most popular Lisp interpreter, doesn't even use Readline, so you can't use the up-arrow key to bring up previous commands and re-run them.
clisp does it, but people seem to be talking that one down. God forbid you make anything user friendly.