It is a matter of age, but not in a matter of "old age". I'm 30 and since I have no actual knowledge regarding your age, I'll assume the same for you.
I have a house, a job, a car, a wife and two kids. I can devote at best about 10 hours a week to ALL my games. The people you're playing with (by and large) can devote double that to a single game.
There is no way you'll ever progress to their skill level. It can't be done. Boredom is a young persons problem.
If ever you're feeling bad about your skill, break out an old fighting game that you mastered, and play somebody younger. I can't hold a candle to a kid playing COD or the fighters. But I can still lay waste to the kids in Virtua Fighter 2 and Soul Caliber.