I don't know why Riot keep nerffing tanks

Well, that's what I conclude from playing several days with the new runes system: tanks are stupid, like the meat on the table, waiting for adc and ap to eat, and cannot fight back. Tanks now do 0 damage, because if you choose the tank runes path, you got literally 0 ad and 0 ap when you start, and of course, no lethality. If you have tried different combinations of the old runes, you know how import the initial ad and ap from runes are for the early game damage. Now, 0 for tanks. Also, if you have tried the lethality old runes, you know how good they are for mid game damage. Now, 0 for tanks. Additionally, I feel the new runes are stronger than the old runes and masteries, except for the tank ones --- I would definitely want a straight shield instead of the funny Aftershock. BTW, Riot has been intentionally reducing tanks' damage for a long time, starting from the sunfire (it was 40 damage per second), to the black cleaver (it was 50 ad), and to Thornmail (look at how little damage it does now). The most funny one is the change Thornmail: Riot conceal their real purpose by saying we don;t want tanks become constant hp provider for the enemy adc so we give Thornmail "Grievous Wounds" effect. WTF? With the old Thornmail's damage, please tell me, who the heal can lifesteal from a tank?????????? Riot think we players are stupid, don;t know how to do math, so they give this funny reason and make us think Thornmail is not nerfed. SO FUNNY! When I play adc, I used to afraid of tanks, because they can sunfire and thornmail me down, but now, I'm so happy to meet a tank: I can just stand face to face and autoattack the tank, his sunfire and thornmail do no damage and he dies. So funny.