I checked this with my R6RS implementation and it works just as you would expect (https://github.com/maplant/scheme-rs)

(Just me suggesting other alternatives right now)

  ((fn [xs ret]
     (if (empty? xs)
       ret
       (recur (rest xs)
              (+ ret (first xs)))))
   (range 5) 0)

  => 10

Is Racket a good language to pick up and re-learn my concepts + implement some tools? Or are there some other languages that would be better to both brush up and learn the syntax of, I do not want to fight the syntax but rather express functions as seamlessly as I can.

    (define-syntax rec
      (syntax-rules ()
        ((rec (NAME . VARIABLES) . BODY)
         (letrec ( (NAME (lambda VARIABLES . BODY)) ) NAME))
        ((rec NAME EXPRESSION)
         (letrec ( (NAME EXPRESSION) ) NAME))))