After several years of playing I have come to the conclusion that the general populace of players simply refuse to change their playstyles in an efficient manner.
Whether its a new champ with skills no one has played against yet or an old champ that has been recently "tweaked" players just don't like the idea that their old patterns of play might have to be adjusted when changes are made.
Every time a new champ rolls out: OMG they are OP!!!!! Meanwhile the proffessional's are getting as many games in with and against the new champ picking up and learning their Pro's and Con's, Two to four weeks later the players at the higher skilled end of the general populace begin using their old champs against them effectively...a couple of months later the general populace for the most part gets the hang of it. (Some will never be ok as it is easier to constantly complain on the forums than to "learn" how to deal with a new champ or a newly adjusted champ for them.)
Riot has gotten much better at finding that middle ground before releasing a new champ or even tweaking an old one. But the fact remains does it really matter? The term OP is really starting to become short for "I really don't want to try" more than it is honestly Overpowered.