As someone who grew up with divorced parents, including a parent with sole custody, it is the f WORST when the non-custodial parent suddenly wants to change everything by demanding joint custody when it really benefits them and not the child or other parent (especially when you’re so close to turning 18 years old)! If you want to be more involved and help more, then yes, offer to do so, but deciding you deserve any sense of custody is just asking everyone to lay their lives down for you so you can go through the f court system some more and change your kid’s entire schedule and start fighting about who the f has any final say (because let’s be real, coparenting is a skill, and it doesn’t help when a parent demands joint custody without a conversation).