The cycle
Assasin Meta --> Tank meta --> Bruiser Meta --> Poke Meta --> ADC meta --> Assassin meta
Its just a cycle, really. The majority of players in league are meta sheep, Or more accurately, lcs sheep. Example: X lcs player picks X mid and builds frost-queens. Suddenly, its a great awakening about how the item is op, and clearly it has no weaknesses at all. (Not making statement about balance here, Frost queen active pretty busted). Until it is nerfed, and the masses move on to the next op cycle and start playing all the assassins.
Currently, we are entering the assassin meta, where players will whine about Assassins and how they offer no counter play (tanks pls) and how an item that hasn't even been released yet will be op. Assassins will be meta for a while, then we will move into the next meta, where the masses cry op until nerfed.
The gameplay boards complain about one thing, then lose interest until a new change is implemented, then complain again until lose interest.
A problem without a solution is whining, but I guess this isn't really a problem that can be fixed. Its really just a mindset of the majority of league players.
Note: my meta cycle might not me completely accurate, but I feel it conveys its purpose just fine.