When I played WvW it was a huge charlie foxtrot and I had no idea what was going on. So many people and particle effects flying everywhere, I couldn't even tell if I was providing any meaningful contribution.
I've always been a more Co-op type of person anyways.
I think this is normal, until you learn the WvW mechanics, why supply camps/caravans are important, how to build and operate siege equipment, and in general, understand how the whole thing works. At high population hours, it's true, you can get lost in the whole "zerg" mentality, chasing around a big crowd of people, throwing yourselves at the nearest Gate and getting routed in every direction at the first sign of resistance. And you're right; there's no organisation in that, just pure chaos.
But stick around for a while and someone with a bit of leadership usually comes along and starts directing the flow of battle. The majority of time spent in WvW, in my experience, will have you dealing with the defense and capture of various supply camps and towers. Supply is needed for Keeps to upgrade their defenses and build equipment like Cannons and Mortars. Whenever you take over a supply camp, be sure to grab some supply from it, and the next time you come across a building site (commonly, Burning Oil above gates, or Catapults/Ballistas that players are attacking a position with) you can contribute to getting it built. You can also use supply to repair Gates and Walls that are under attack.
I like being a defender. I'll report enemy troop movements over /team when necessary, and man wall defenses like Cannons and Arrowcarts to deadly effect. I don't much enjoy being one of the 'footsoldiers' down below, but in times of need, I'll lend a hand there too. The important thing to remember is that you don't
have to be part of the "zerg" if you don't want to. You can escort caravans, build defenses, and repair stuff instead. And all of that is equally important to the war efforts.