Agree on the REPL and exploratory programming!

But can’t agree on the structured editing side.

I used to do use structured editing (D-Edit on the Interlisp-D machines) and found it annoying, but perhaps that was due to the mandatory mouse use. The structured editing built into emacs is pretty good mainly because it’s an option you can use at any time rather than a single paradigm.

Also the only way to use comments in a structure-based system is to extend the syntax of the language, and that is awful IMHO.

I use the paredit emacs package (not a builtin). The issues you mention are not present.