I don’t know if parent is ‘missing the compiler extensions [you] mentioned’ or is just not addressing them. But I will take a stab: compiler extensions may be neat/effective/revolutionary, but they are unequivocally not a part of a programming language. That is why they are compiler specific extensions. I could code a compiler extension for LLVM that is a conservative, generational garbage collector and have the extension flag be —-no-more-manual-memory, but no one is then going to say that because that extension exist C++ is a garbage collected language.

tl;dr -> compiler extensions are by definition not part of a language, no matter how useful, and therefore do not count towards the argument.