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.
> Python supports all of Lisp's essential features except macros, and you don't miss macros all that much because it does have eval, and operator overloading, and regular expression parsing, so some--but not all--of the use cases for macros are covered.
Macros are a huge part of Lisp. Were they not, I don't think you'd see Lisp programmers defending the bare bones not-syntax so fiercely.
For what it's worth, if you get good at a language, you start decomposing things into trees yourself when you're faced with some tricky code.
*Actually, I'm not 100% sure that this is true - it would be more accurate to say that I am not aware of any other language that can be used to produce an arbitrary s-expr, but that such may indeed exist. If anyone can correct me on this point it would be much appreciated :-)