"Lisp is not a good user interface."

this is a fallacy. Lisp is an excellent user interface, for the right kind of user. Knowing who you are designing for, or more generally, what expectations you are trying to meet, is critical. No doubt Lisp is a poor choice of user interface for a large majority of users. But most programs do not target "most users", rather a small subset of users with particular goals, workflows, skills and needs. For them, Lisp might be just the right thing.