> The machines invented so far haven't done "highly innovative things" all by themselves, and yet people doing innovative things often find their machines useful.

This statement is near to being tautological. The central test is rather whether people who do "highly innovative things" become more productive in doing so not just by the mere fact that the AI removes some yak shaving from their work.

Otherwise, you could simply argue that people who do "highly innovative things" also find

- a housecleaner

- a personal secretary

- using a word processing program instead of a typewriter

- a washing machine

- an automatic dishwasher

- ...

to be useful.