Is it possible that the folks you are so fed up with, are doing the best they can with something they shouldn't have to be dealing with at that age?
My 15 year old daughter and 21 year old son were killed in a car wreck at the end of August. The kids came out of the woodwork from school for the funeral. Some sang in the choir, a couple played and sang both my son's and my daughter's favorite songs.
They did the counselors there to talk bit at school for those who wanted to. If you looked at it, I suppose you could say it was overkill. I don't know. I figure people were doing the best they could with something that there is no correct way to deal with.
I didn't see it as a popularity contest, as my kids never ran with the 'popular' crowd. Did some folks seem to 'cry' louder and longer then others? I suppose. But it's such a goofy unreal thing that I can't be angry at them.
That being said, there is no script for how someone mourns or deals with death. I know my wife, my surviving daughter and I all deal with it differently. For me it's a much more solitary thing, late a night when the house is quiet. Then the emotions come out and I can let myself feel the pain.. I can't talk about it yet, outside of typing like this. My daughter doesn't want to accept it at all. My wife talks about it often. I don't know that any of us are doing it wrong.
I remember back when I was a senior in High School, the gal I took to senior prom was killed in a car wreck a week before graduation. I remember seeing a lot of what you saw, and wondering why I couldn't feel that. But it was too surreal to me then. It didn't make sense and I couldn't put it into a slot that let me understand that someone so vibrant and with so much going for them could be gone just like that.
I'd suggest not worrying about the others, and allowing yourself to mourn the person that clearly has affected you with their death.
The others are allowed to mourn their way, you mourn your way.
No explainations needed.