I am so tired of the entire "muh frontal lobe is not developed" argument.
We do not measure rights by IQ. It never was about the brain size, and if it was, then by 40 we should start removing rights again, since the frontal lobe is at the smaller power level again.

Just accept, that humans will never be a 100% efficient machines. You have right to have an opinion as an 8yo, and you also can do SOME decisions at that age. And that opinion will not stop developing by the age of 60. Humans are fluid beings FFS!!!