[euyyn]

> They keep you from being sued [but] at what cost to the participants [...]?

The people suing you would be the participants, because you would have already harmed them. Not getting sued by them is just a derived benefit of the primary goal of protecting them from you. And the protections extend well beyond what a patient might bother suing you for: it's an ethical committee after all.

> at what cost to less well equipped researchers and at what cost to science itself?

Completely secondary considerations, for very good reasons. Nazis weren't the only ones to harm patients; also well-intentioned scientists that thought of the greater good for science itself, and grad students that lacked resources or equipment.