Nothing's really beneath me, so I'll take a crack at it.
1. The sophistication of teamwork has grown immensely. Whereas once upon a time the honors went to whoever could hide well and shoot well at the same time, now, coordinating movement and firing, handing off suppression duties, and controling an opponent's perception of the field are needed as well. The list of team actions is longer than that, really, but I list those as examples of the advent of actual tactics in paintball.
2. New skills are being added all the time, as old skills fade from relevance. Crawling is less useful now than it once was (although there is still a time and place) while slides of different kinds are far more important to making moves.
3. Fitness is required to a greater extent now than nine years ago. Two weeks of getting accustomed to physical demands might help, but there would still be much catching up to do.
4. Reaction speed, I argue, is an acquired attribute. Snap shooting is far more advanced now than back in the day, and a few good snappers could establish dominance against old school teams and press that dominance to obtain control of the opponent's perception of the game. At that point, the snapper equiped team runs over the woodsmen.
5. Those classic teams that are still around aren't really ten years older than they were ten years ago. Well, the team is, but the players aren't. SC Ironmen keeps bringing in new talent (Bob was still the captain in '94). I'm not saying that replacing Bob made them more competitive, I am saying that Lessons learned have been passed down, not kept in the minds and muscles of the original players.
6. A fallacy: two games that look the same to an observer are equal.
Watch Cartel vs. Brass Eagle All Stars, then watch Naughty Dogs vs Lockout. The games are not all that different. Now put Naughty Dogs against BE All Stars and Cartel against Lockout, and learn the difference between Pro and Am. The difference between the '94 teams and the '03 teams is analogous. If someone doesn't like my choice of teams in the example, replace them with other teams of the same caliber.
7. A question to Mr Rubin: Can the accomplishments of the last ten years all be obtained in a week's time by a team fresh from the time machine? Ten years of developement are all external to the player? No disrespect intended, but I don't agree. Persuade me.