I partly agree with you, because some players on public servers are selfish and they focus their skill only on getting the most of XPs. But this is somehow the gameplay of Enemy Territory is. What make you earn most of XPs is what developers has expected you to do in the game. And all you can do to earn XPs is to accomplish objectives. You can't really complain because a mate gives you ammo pack each time you respawn.

Teams, championship and ladder are a great alternative. When you want to practice, aim and kill some people or just having fun, go on publics servers. But if you want to play more seriously in a team with teammate you like and who plays the same way as you do then, play matchs !