I think it's just that people all play different roles so when their role is countered, they're up in arms. Think back to the beginning of the season in the assassin meta. It was TERRIBLE! But the people who were complaining were tanks and ADCs because their builds did nothing to stop the assassin's lethality and they would just get one shot respectively. So what did Riot do? They responded with nerfing Lethality, changing around tank items, and making Crit items for ADCs cheaper. Like do you remember when tanks would just build Deadman's Plate and Spirit Visage every game and then just run around like a monkey? I do because I played tanks last September/October and if you Built Randuin's over Deadman's you would get flamed for being an idiot. Now you actually have to think about what to buy as a tank? Is Deadman's best? Or is Thornmail or Randuins? Should I get Spirit Visage? Or do I need Adaptive Helm or Abyssal Mask?
Getting back to my original point: people who are complaining now about the tank meta: Mages, Assassins, and ADCs. Mainly because tanks do percent health damage (to deal with other tanks/actually deal some damage in a fight), pack a lot of CC and some tanks (cough cough Cho'gath) can still one shot them every 90 seconds if there are enough enemies around. My prediction: Season 8 will come out with a large-scale rework to Lethality and Magic Pen items, we will get another pair/aura item that eventually brings tank supports back to the meta, and hopefully they don't touch champions but will fix some numbers regarding tank items.