The GP is factually wrong. There's plenty of empirical evidence to indicate that language influences thought, and that syntax is therefore important.
Although, I would point out that while your argument ad absurdum is generally reasonable (the fact that syntax can make the difference between a very good language and an unusable one), whitespace and malbolge also have terrible semantics that contribute to them being unusable.
As a former Lisp enthusiast (and still an enjoyer), I'd actually use my own darling as an example: Lisps have amazing semantics and are generally good languages. Their syntax is highly regular and structured and easy to parse...except that it's brain-hostile, and I'm convinced that it actively makes it harder to read and write - not just adopt, but actually use.
Although, I would point out that while your argument ad absurdum is generally reasonable (the fact that syntax can make the difference between a very good language and an unusable one), whitespace and malbolge also have terrible semantics that contribute to them being unusable.
As a former Lisp enthusiast (and still an enjoyer), I'd actually use my own darling as an example: Lisps have amazing semantics and are generally good languages. Their syntax is highly regular and structured and easy to parse...except that it's brain-hostile, and I'm convinced that it actively makes it harder to read and write - not just adopt, but actually use.