Since you've taken the worst possible interpretation of his comment: He's saying that clojure errors are not user-friendly and give you little idea how to implement a fix.

I agree with him, and I have spent a lot of time scratching my head debugging clojure.

Python gives a better idea of what's wrong, where it's wrong, and what a fix might be.

Here's roughly his example, but in python:

    >>> "a" + 2

    Traceback (most recent call last):

       File "<stdin>", line 1, in <module>

    TypeError: cannot concatenate 'str' and 'int' objects

in the Lisp I'm using I get this:

    CL-USER 24 > (+ "a" 1)

    Error: In + of ("a" 1) arguments should be of type NUMBER.
      1 (continue) Return a value to use.
      2 Supply a new first argument.
      3 (abort) Return to top loop level 0.

    Type :b for backtrace or :c <option number> to proceed.
    Type :bug-form "<subject>" for a bug report template or :? for other options.

    CL-USER 25 : 1 > 

There is a clear error message and direct ways to fix/report the problem. Including another REPL to investigate the error.

CL Loop-macro error reporting is legendary:

    [1]> (loop until sun dies and moon explodes)
    *** - LOOP: illegal syntax near DIES in
        (LOOP UNTIL SUN DIES AND MOON EXPLODES)
    The following restarts are available:
    ABORT          :R1      Abort main loop

Python is most advanced:

    >>> [if dark then moon else sun]
      File "<stdin>", line 1
        [if dark then moon else sun]
          ^
     SyntaxError: invalid syntax