You could absolutely randomize care between a doctor and an AI under an IRB. I’d be stunned if there aren’t a dozen studies doing something like this already.

You have to justify it, but most places have sections in the document where you request review to justify it. It’s not any different from giving one patient heart medicine that you think works and another patient a sugar pill.

Huh? Do you have any actual examples of such studies? I don't think you understand how IRB actually works.

In actual heart medicine studies the control arm is typically treated with the current standard of care, not a placebo. So it seems pretty clear that you don't have any actual knowledge or experience in this area.