I think overall I see two glaring complaints over the past few months.
- Tanks feel worthless.
- ADCs feel too powerful
This leads me to believe overall, ADCs have reached over the top levels this season. I think the complaints generally come from the fact that ADCs have become solo-capable champions too early in the game now, which is a fundamental flaw when having a champion designed as they are. At least in seasons 4-5, ADCs became solo champions late-mid/late game but before then, were weaker than any other carry role and rightfully so due to having an entire class designed to equalize or even push ahead their total power.
Now ADCs are hitting their equal power rating with other carries often in the early-mid to just mid game. This is why Corki and Varus mid were staple during MSI, why Lucian mid and top are becoming great picks. Out of any carry role, ADCs are the most dangerous when too strong due to having the support class assisting them and the nature of the build paths and range they all boast. There is no counter to an ADCs damage output. There's only the option to simply kill them before they kill you. Armor does not work. The best tank build, save maybe a 6-armor Rammus or malphite, will always melt to the best ADC damage build, or even just an average one really.
I'm not hating on ADCs, just pointing out what I've seen on various forums, videos, etc and adding my own little spin on it as well. I overall have seen most complaints going towards ADCs, filtering out the constant Yasuo hate that has been spammed since he was buffed out of uselessness after release. It's also not the general class, it's the top contenders in them. Someone like corki or Ashe right now aren't crazy, even as ADCs. But Cait, Twitch, Draven? They are shredding everything. But when an adc becomes broken, they ruin the game far more than other classes due to their damage smashing squishies and still crushing tanks. Assassins at a broken level are oppressive towards squishies, but not tanks. Tanks being too strong aren't oppressive generally to mages or bruisers, only assassins and ADCs. And so on and so on. ADC is the only class that is oppressive to all, even assassins (because of the support class), when broken.
Just my two cents.