Damage Creep

Creep, as in it creeps in slowly, without most noticing the gradual shift. In all it means damage in the game has risen over time, at first without notice, but now that it's become a problem people are starting to see it.

It's a product of "power creep" that exists in pretty much any long running persistent game like MMOs and MOBAs. New stuff (items, abilities, characters, mobs, and etc) are added to the game; they have to be bigger and better than before. This leads to an overall game increase in things like damage, mobility, survivability, resource generation, and whatever else in the game mechanics.

Its a myth that people create to help themselves feel better about being bad. Nothing has really changed with damage in this game. Mages lost the three 120 AP items, got a 5% bonus AP compensation and TLD, they also lost the active from DFG, which allowed any mage to one shot people. ADCs lost a lot of AD from their items, but in return they received fervor. So the damage is equal if not less. As for tanks they received damage buffs. They got a buffed Sunfire Cape, GotUD, and buffs on trinity force. Not to mention the buffs on tank items stat-wise and cost-wise. So when Riot came along and made BC viable again, and then buffed LW upgrades to viability the tank mains who were used to not taking any damage all of the sudden started to, although still not enough...Anyways I could explain a lot about the current state of the game and how its changed, but basically Riot made tanks OP, and had to make a bunch of changes just to fix the meta.