With that many people on the field, gameplay is fast and frantic. Experiencing that as a first-timer, especially one not familiar with actually using their gear in the field, can be quite overwhelming. At BW2, I only had 2 skirmishes and 1 milsim under my belt. I was still quite a noob, but at least I understood how my equipment worked, and had a bit of an understanding of working as a team. When I got together with the RDF in the afternoon, things went really well. But based on seeing what some of these first timers were going through and my own experiences that morning, had BW2 been my first game, I probably would have hated it.
Look at it this way - going to Border Wars as your first game is kind of like racing in the Indy 500 when you just got your driver's license.
Oh yeah... and what m102404 said... lol