I think they are just lazy and don't care. They have no incentive to make meaningful changes, because enough idiots give them money despite the balance being an epic fail and on top of that Riot having the audacity to dictate how they want players to behave (like don't say ANYTHING negative ingame LMAO).
Runes reforged should have been scrapped immediately and reworked into something that makes sense.
The whole juggernaut concept was just broken from the very beginning, should have also been scrapped.
Healing was NEVER properly balanced, because Riot uses INSANE debuffs instead (GW 40%/60%), it's just a really lazy bandaid fix.
Same shit with defense, RIot NEVER balanced tank stats. Void Staff and Last Whisper, Cleaver are way too good, but instead of tuning everything down to make it less binary RIot keeps adding even more broken shit like Randuins to reduce crit by a certain percentage or Adaptive helmet to reduce magic damage by a certain percentage, Steraks, Gargoyles.... etc etc. effects that should be situational but end up being the most reliable defense in mid/late game.
And then ofc they can argue that damage didn't actually increase, because there is actually powercreep for everything, not just damage. It makes the game feel extremely binary, it creates way too many hard counter scenarios where the game just feels pointless to play.
Riot keeps making changes just to keep the game changing, they never had any consistent vision how the game should be balanced.
They keep adding fuck ups to the game and consequently refuse to revert obvious fails immediately, instead they focus on controlling the narrative and doing small placebo changes, but the fundamental issues always stay.
Just look at how long it took them to make another Mordekaiser rework only to come out with another juggernaut design that is even more broken then the season 5 version. They didn't learn anything at all.
And then you have Sett which is basically the personification of juggernaut powercreep, cynically also called "the boss".
Changing a few things here and there is obviously much easier than to carefully reassess the balance of all champions and items on every step to try and fine tune the game.
I think the best way to describe Riots design philosophy is: an amalgamation of conflicting and inconsistent power phantasies that can't work together in a balanced game.