The biggest problem league has in terms of balance
At a very simple way of describing it is that lane bullies don't fall off nearly as hard as they should. Even traditional lane bullies like Pantheon and Renekton can still straight up solo carries and trade 1 for 1 at almost every stage in the game. And while that doesn't happen nearly as consistently as it would during their largest power spike in the mid game, they are still a consistent threat to always do this. In past seasons however, this wasn't always true.
Some of what I blame this on are keystone masteries making damage so absurdly high that it doesn't take much to kill anything short of 200 of both resists plus 3.5k hp. Another thing I blame is all the stupid amounts of flat pen ADs can stack and use to blow up squishies and basically so true damage to them since they aren't going to be itemizing much defense.
The other part of this same problem is many late game power houses actually end up being really oppressive laners. Azir is a the poster child for this but he's hardly the only champion guilty of this. This applies to champions like yasuo, graves, Illaoi, fiora etc.
How can you balance a game where the best laners are also tending to be the best scalers? Why pick anything that needs time to ramp up when it'll be denied to hell and back only to barely outscale it's opponent? This is why the same group of champions constantly rotate in and out of being meta because you nerf one group and the old group just re-emerges.
I feel like this needs to change. I feel like late game scalers who traditionally suffer from poor lane phases need to actually have incentive to be played because currently many of them aren't worth picking when lane bullies scale almost as well while being able to provide non stop pressure from the very start of the game.