I think "plagiarism" refers to taking credit for the work of others. Using other people's work to make your own isn't "plagiarism" if you give credit. This doesn't mean AI is good, just that "plagiarism" isn't the correct word.
This is different from saying "If you don't give credit, it's plagiarism."
Put another way: it is sufficient for something to not be plagiarism if all materials are credited, but that doesn't necessarily mean everything that doesn't do that is plagiarism per-se. It is beyond the scope of my musings to reckon the minimum requirement of non-accreditation for something to qualify as "plagiarism".