Just as in ET, the gameplay dictates what people need to play. To win, you’ll need some of everything, I’ve nearly always played engineer, probably will continue. Others will play FO or Medic, but to win…you need everyone. Afaik, there’s no uber weapon for either side to worry about
These are called weapon limits, causing a certain class to run out of supplied weapons.
It is possible to configure it in W:ET, but as Nail pointed out, it’s no use to wait for those weapons.
Although you could use a panzerfaust in W:ET to take out a whole group of people, it was never considered a problem to lack one and people just took another class.
But as said: it’s a setting, so you can do with it what you want on your own server.