Can you say more? Guile's the only scheme I've tried (attempts at packaging for Guix). Debugging has been difficult, but I figured it was me struggling with new tools and API. Does racket have better facilities for introspection or discovery at the REPL?

Yes, since years, all the way when it was still known as Dr. Scheme.

It has a graphical experience similar to the survivors from Lisp is Great days, like LispWorks and Allegro Common Lisp, or Clojure with Cursive.