I don't have any particular words of comfort I'm afraid, but just wanted to pipe up that I know exactly what you mean.
My dad died very suddenly and unexpectedly when I was 15. It was a hellish time (34 years ago though), but I did whatever I could to try to support my mother through the initial shock.
My two eldest DCs (now 25 & 16) are hugely empathetic - I'm interested in their lives and, equally, they're interested in mine.
I started a new job today - both messaged me to send wishes, etc.
My youngest, DD(nearly 15), has just been kicking off yesterday and this morning, because my working hours are now inconsistent with what fits in with her plans - mainly around providing lifts/money.
I arrived home earlier and, no sooner had I stepped in the door, she was complaining about her lot.
Op, I agree, teenagers aren't inherently selfish by nature. My eldest two aren't remotely selfish, so it's presumably not a parenting issue?
Sorry, no words of comfort. But I get you.