This is so American centric, but more to the point, coming from a highly privileged (mostly classist, cisheteronormative, and ableist) point of view - it isn't just the drinking age (in the UK for example it's technically legal for a child as young as 5 to consume alcohol), but it's mostly the fact that a lot of people have been responsible for themselves, and often others, potentially from childhood because they/we literally have no choice - being disabled, having a disabled parent or sibling, losing your parents or guardians at a young age, being kicked out for being queer, being kicked out for being disabled, losing your home due to poverty, not having parents or guardians around to do the caring because they're too busy working 3 jobs to make sure there's some food in the house, and so on and so on (from living in a war zone to experiencing kinds of trauma and abuse I've not already mentioned)..
When you consider all of those, and as someone who has/is living a few of these situations myself, the idea of being "fresh" at 30 (which was a while ago for me) is not only absurd beyond words, but it also erases all of the hardship, and achievement, of making it to 30 despite all of the hurdles in the first place.
So sure, if this take makes you feel better about your age - great, but it's more important that it serves as a reminder of how fucking privileged and lucky you are to be able to hold that point of view.
The post is clearly referring to the legal drinking age, driving age, and age of majority which are 15+ pretty much everywhere. You are bending over backwards to get offended by this.
That's really funny see, because your comment doesn't contradict anything I said, perhaps apart from the American-centric part (though nowhere does op support your idea that they mean 15 as the drinking, driving, whatever age), so it would seem that if anyone is offended here, you are, by the first sentence of a comment you didn't even bother reading properly, never mind comprehending, because it included words like "privilege" lol
You got butthurt about the word "responsible", when in the context of the post it is logically referring to being legally responsible for yourself (by following a list of two other legal privileges), as in having the legal authority to make decisions for yourself while you took it to mean just "having responsibilities" and got all worked up about it.
I hope this clears things up for you, and that you can apply better reading comprehension to avoid these kinds of episodes in the future.