If you only rewarded the best PVP or PvE players no one would play. All players have a chance to get good loot at the end of a match. The completely random nature is what keeps casual players playing in crucible. It give players incentive to run Nightfalls and raids. The best players dominate in crucible. They earn more marks and more exp. The best PvE players start making friends and it's easier to run raids as a group. I have carried lower level guardians through nightfalls and they sometimes get the exotic weapon. I will get energy. RNG is gambling. Either be happy about rolling the dice or don't play the game.