Haha, AI can't do $THING

>Sure, AI can do all of those things, but the dirty (not so) secret is it can only do it because it has had a large corpus of human creations

That's how human creativity works, too.
All inventions (technical, nontechnical, philosophical) work that way.

There is no fundamental difference between a human brain that learnt from existing works (school, university, life) and produces (extrapolates) new things and an AI doing exactly the same thing.
Currently AIs are not very good at extrapolating and therefore not very good at inventing, but I don't see this as a fundamental limitation.