Jungle Difference

How is it even possible for your jungler to come out of the laning phase with half the farm of the enemy jungler, when the enemy jungler has been ganking all game? Why are these people even allowed to play jungle in ranked? It's infuriating to no end how a bad jungler is absolutely catastrophic to your chances of winning, when a bad player in any other lane at least gives you a chance to pull out a win.

If one enemy laner is crushing it, all you need to do is get ahead, and the teams are even. There's agency there. If the enemy jungler is crushing it, every one of their lanes is ahead and the game is over. There's nothing you can do as an individual. You can't take an advantage and roam with it anymore. The enemy will just push the wave, get a plate, and get just as much gold as you would from getting a kill.

Why is the jungler being the central and most influential member of the team still a thing?