Any language adopting s-expr would instantly be called a Lisp.

Arguably, the s-expr syntax is what enables the rich code-as-data metaprogramming that you find in Lisps. Working with full macros in a sexpr language is already complex enough, the an extra layer of complexity that non-sexpr language add really breaks that camel in half. The point is, you really need code == AST parity to make a powerful macro system workable. You don't necessarily need the parans, but complaining about parens is really missing the point.