Better syntax highlighting immediately comes to mind. Maybe code actions/automatic refactoring too.

Lisp does not have that much syntax for highlighting to be a problem.

Lisp is also a symbolic language. Meaning the code work on symbols, not data, only at evaluation the value of the symbol is known. There’s a lot of symbols manipulation routines like macros, intern, package loading,… that prevent to statically know the code.

It’s why people use the REPL flow.