Why is the adc role treated in such a cruel manor?

As a former adc main I don't understand why Riot have treated the adc class in such a cruel manner. I feel as if tanks have been receiving all the love lately due to how strong they are. Throughout season six tanks have constantly been know as the most overpowered class while adc's have limited options to deal with them. Due to the assassin update a lot of adc armor penetration builds no longer work due to the item changes leaving the adc mains that are up against three tanks on the enemy team less options. On the other hand tanks have yet another weapon added to their arsenal, courage of the colossus which is without question overpowered that allows them to survive even longer giving them a MASSIVE shield that simply feels unfair. I have been in countless amounts of games where a tank builds no damage items yet still does the most damage in the game. My point is tanks are receiving loads of love despite them already being extremely powerful while adc's struggle to deal with the assassin and tank meta. My hope is that Riot realizes this problem and buffs the adc class as a whole in some way shape or form because I feel as if the adc class is the weakest of them all and it makes me sad having to switching roles just so I can climb the ladder faster. Perhaps if Riot introduces new adc items geared toward destroying tanks, buffing their items, or lower the cost of their items would help adc have more of an impact in the game.