Right, that's the problem. The fact that doctors must ask for the consent of people who don't understand what they are consenting to.

The idea itself isn't that controversial - age of majority laws for contracts, voting, and even medical treatment clearly acknowledge the idea that some people are too young to know what they are agreeing to, so the decision should be made by someone else who takes responsibility for them (most things), or there should be no decision because there doesn't need to be one (voting).

We just need to refine our understanding to reflect the reality that as old as you may get, you will never understand some things.