I haven't posted in a long time, but this is something I wanted to chime in on as a long time on and off player since before season 1 (November, 09).
Disclaimer: I am not good, I make no arguments that I might be good, this is merely based on observation, not opinion.
This is not the first time people have clamored that damage was too high, or to stop buffing people and start nerfing them. This has been a flip-flopping issue since the inception of LoL (Who remembers the terror of 09 Twitch?), nor would it be the first time that the opposite is true. In fact, we're in this current state because of the opposite. Is our memory so short that we don't remember having to build atmogs on everyone and their mother?, or tanky brand? The times when % damage and true damage were the only useful damages because everyone was so tanky that not even assassins could 100-0 an ADC.
I'm not arguing that you're wrong, or that league is in a healthy state. I'm just stating that this feels a lot like a repeat of the past 9 seasons.
Disclaimer: I am not good, I make no arguments that I might be good, the following is based on the opinions of a nobody.
My opinion is that the same issues we've always had are still the issues we face today. The lines between roles are too blurry. Tanks deal too much damage, they should be CC machines, but they should never come out on top in a 1v1 against a DPS.
DPS/assassins should not have survivability let their survivability rely on the support. why does banshees and GA exist in their current state? Why can everyone and their mother blink, dash, leap, jump, hop, skip, and vault over the nearest wall?
Scale defense on tanks harder and tone down their damage, make defensive stats less effective on damage based champions (this can be done by dramatic base stat tweaks with % stat increases on items, or any other number of ways), give bruisers poor scaling, but high base damages, with defensive stats that sit in the middle, etc. It doesn't feel that complicated. The most complicated part would be the overhaul needed on the items to match the changes and give reasons for certain types of champions to pick certain types of items.
Who knows though, maybe I'm wrong, that's always possible, and I welcome rebuttals.