I see what you mean. But I don't think that's what he meant by Lisp.
After all, if you believe that, then Python is a Lisp too[1]. And when people say "Lisp", they don't mean "Scheme and CL and [...] and Python".
Sure, like any class of languages, there is not a single syntax. But every lisp has a syntax. And the languages people associate with the class "Lisp" use parens. And in many peoples' opinions, there are better ways of representing an AST. Like indentation, for example. Or curly brackets.