Let me give it a try, from an abstract/Emacs point of view:
Emacs is good for Lisp development, but both “raw” Emacs itself and most of the packaged customization versions (Spacemacs, etc) are fairly ‘opinionated’ about Lisp, and that opinion usually falls close to: Lisp is great, but Common Lisp is a little/some/much too much, so our choices often lean away from CL’s. (Lisp-1 vs. Lisp-2, dynamic vs. lexical scope, etc.) This means that you’re customizing in a nearby language, but one that dislikes some of the things that you liked when you chose CL, so there’s some impedance mismatch going on.
That said, you can get a great CL dev environment from Emacs, but you’ll want to install a bunch of add-ons first, probably including a non-Emacs lisp interpreter and a package to bridge Emacs and that other lisp. True fans of CL would really like a full-blown Emacs with real CL at its core, and periodically people try to make those (Hemlock, etc), but they usually don’t catch on.