Exactly, a usable structure editor is extremely difficult to write. The problems with Lisp are that your source code ends up flattened into plaintext in the en

Exactly, a usable structure editor is extremely difficult to write. The problems with Lisp are that your source code ends up flattened into plaintext in the end, and that identifiers and symbols must be resolved by string lookup; there is no "first-class" reference, just a collection of resolution rules and environments and symbol manglers. You could fix these, but you wouldn't really have Lisp anymore.