Why am I not seeing tanks when 7.09 is out

Naturally, you'd think everyone would be playing tanks but I've only seen a couple. I play amumu if we have no teamfight and I still need to try the new gargoyle stone plate oh him. It makes sense since he dives in and pushes r so that way when the stun ends, he uses it and he can't die for 5 seconds. There's also an exploit where Vlad can use it to get down to 0 HP so he can't die. Zac's ult looks insane and I don't know why people aren't picking him. He picks people up and brings them to his team. How aren't people picking him. Sejuani has quite a bit of damage for a tank. Not as much as a bruiser but still alot. Are people still attached to their carry jg's or do people just think tanks are not fun.