Lack of balance between Damage and Resistances

We've seen a rise in popularity of Tanks, Tanky fighters, and champions that are damage dealers but build tank items to remain useful in the late game. I think this has happened because most higher level players realized that it's too dangerous to build full damage whereas tanks can outlast their damage late game and proceed to carry by building nothing but resistances. We're seeing a rise in tanks/tanky builds because damage just isn't dependable if you just get CC'd to death and outlasted in an engagement with a tank.

An example can be seen in Ekko, as people who know AP Ekko takes a lot more skill to play than Tank Ekko, because 1 mistake late game can cost you everything. The same goes for most assassins. While it may not be an assassin's job alone to carry his team, people build tank items because it's no longer smart to put all of the marbles on the ADC or the one person whose fed.

There is a fundamental imbalance between tank-champions and damage-champions in this game. If there is an Assassin rework coming up soon, I hope it will address the issue of late game dependability of assassins (without needing to go tank).