> With LISPy language there is almost zero syntax

To be pedantic, this isn't quite correct. Syntax isn't countable like that. What S-expressions are light on is production rules. At their most basic they have IIRC 7 production rules but there are absolutely 0 languages based on s-expressions which are that simple, since it doesn't give you anything like quasiquotes, vectors, Lisp 2 function resolution, etc. Reader macros make matters much worse.

What we can say is that they are constructively simple, but not particularly unique in that. Once you get into real sexpr languages they aren't simpler than horn clauses, and are constructively more complex than languages like Brainfuck and Forth.