I'm confused by your first sentence because it is setting up a straw man. Both the Cass report, and current standard of care affirmative gender care tries to identify and address other causes of mental distress, and I'm not aware of program that profess that the gender reassignment process is designed to, or will alleviate that.

Kids of 18 are allowed to vote, join the army and kill people, and drive automobiles, even though many of them don't "precisely know what they are doing".

Again, it is largely a false narrative that clinics are systematically forcing kids who are questioning themselves along this pathway. Only a very small minority, who express firm and consistent conviction in their assessment of their gender, traverse this path.

Thank you for providing the reference to Jamie Reed's opinion which seems to refute what I just contended. But until I see widespread evidence to support their claim, I will stick with my stance. If their experience were representative of the field, then one would expect that gender clinics would be proud to post that a majority of their clients end up transitioning, and I'm not aware of any that claim that is the case.

There is overwhelming evidence from many adults who are transgender that their sense of their gender arose in early childhood and did not waver for decades and decades.

As I point out, the fact that a very small minority of individuals change their minds is not reason to reject the current system. It would only make sense to do so if those wishing to detransition constituted a significant portion of that population. Taken to the reductio ad absurdum level would mean that any procedure that resulted in any harm or regrets to anyone should therefor be banned.