Skill isn't something that is just there with you rather it is something that has developed.
Each person can be skilled in way, those of us who have been playing for years may be skilled in a few or probably all the heroes.
Lets take me and you for example,
some say I'm skilled in assassin, some say I am in scout.
Some say you're skilled in tank, from what I've seen you're fairly skilled at commando.
Skill in this game would mean how good you can use a specific hero and how much better you can be that the other player in that hero.
Rja, UM.. Excel in gunner
Mah, invi,. excel in assassin, mah is better at scout.
Slim, excels in tank
They are all skilled in their own classes, or more better put, classes they're comfortable with.