Doing a farming loop is in no way an exploit. In no way is it not meant to play the game. You need materials to upgrade weapons and armor, hence the farming. Bungie left the option to trade materials in for those who want for marks, hence the attempt to make it more efficient. It's farming, how is that an exploit. farming is completely the way this game is meant to be played, as there are more ten one way to play the game. If you want to focus on PvE but want armor that's locked behind the crucible, it allowed a way to achieve it.