I recently tried learning CL, and was dismayed at the tooling.
While Emacs + SLIME seems to be the recommended way to go, yielding great experience; I could not realise that because I could not get SLIME to work with EMACS, and couldn't get any help in resolving it.
This was after having it work on a previous macbook. Then changed the laptop, tried installing it and got stuck. Led me to give up learning it at all.
I'd like to add better onboarding to the list of things to improve