But that's exactly the root of the complaint. Because there's (for the sake of argument) only one syntactic concept, there's no bandwidth for structural concepts to be visible in the syntax. If you're used to a wide variety of symbols carrying the structural meaning (and we're humans, we can cope with that) then `)))))))` has such low information density as to be a problematic road bump. It's not that the syntax is hard to learn, it's that everything else you need to build a program gets flattened and harder to understand as a result.

Even among lisps this has been problematic, you can look at common lisp's LOOP macro as an attempt to squeeze more structural meaning into a non-S-expression format.