So I know I'm going to get skewered for chiming in on this but it is a personal bias I honestly have and I'm sure I'm not the only one with it. I have a hard time sanctioning self-deliverance for teenagers, because their reasons for wanting to go are often times (but not always) based on problems that are transient and can improve with time. I have many times read on SS about teens who want to leave because of a breakup, loneliness, grades, body dysmorphia, being a virgin, being ugly. The feelings around the despair, isolation, and pain is very real and just because you're young doesn't mean your pain means any less.
But... What I have a hard time with is that developmentally speaking, you're still an adolescent until you're in your 20's. Your brain is still developing (barring any neurodegenerative issue) and things along the lines of emotional regulation, critical thinking, self identity are still developing. And there hasn't been a lot of time to measure any real progress. I think that's why people don't think a teenager can make a rational decision around self-deliverance. I do think that teens deserve a forum to talk about their suicidal thoughts like anyone else and have a safe space; ambivalent about whether it should be mixed with adults though.
I do think children and adolescents with terminal or incurable diseases should unilaterally be able to qualify for doctor assisted, regardless of whatever the fuck their parents think.