Ideas on how to fix it... all of it
Everything is ruined, the sky is falling, godzilla is eating our families and it's all because of rito geemz
nah but really I've had some thoughts
Remove keystones, the more interesting effects included. They generally amount to "More ways to 1shot people" with a few exceptions
Increase the variety of lesser runes, Remove all raw damage/defense runes and replace with situational bonuses or interesting effects, things like celerity are cool, things like eyeball collection aren't
Arguments could be made for some runes on either side, but ultimately if it doesn't actually break a dimension in the game it should be gone, if it amounts to nothing more than a stat stick then it should be gone
Keystones that could be done as runes: Looking at transcendence I see a rune that actually functions in an interesting way because it opens new builds, you couldn't go some builds because cdr overflow would result in nothing more than wasted gold ergo weaker builds. simiilar things could be done with other capped stats such as attack speed, or often wasted stats such as mana
Make tank items relevant:
thorns gets a buff, rageblade twice as hurty.
Three new tank items:
Mirror shield MR anti spell version of thornmail that has an active which reflects a spell similarly to a fiora parry HASAKE recording: It's a yasuo windwall ona HP item Ol Faithful:Converts all true damage to the primary damage type of the champion hitting you, so vayne would deal %physical instead of %true, etc etc
four new tear items:
+1k gold: Get % of mana as HP, on full completion can activate to take a % of damage to your mana pool instead
Gain % mana as MR, On completion can activate to slowly drain %mana while increasing MR by 3x that amount
gain %mana is Armor, can activate to slowly drain % mana while increasing Armor by 3x that amount
+2k gold: Makes you faster based on your max mana, activate to lose mana rapidly to gain speed
Tear items can be upgraded by choice, when a tear is full you can "activate' one tear item in your inventory to evolve it
Champs this could be an issue on:

need reworks, could be nerfed accordingly
Causes issues with everything and should just be watched
Other itemization
Items could be in sets, Every item could be assigned 1-2 of 5 different colors, items of the same color codes grant bigger bonuses, Five 'gold' items (adc items) could grant increases a/s or crit damage, five 'red' items (assassin items) could grant additional movespeed, lethality and AD, bruiser items (Blue) would be along the line of sustain, HP, damage.
Transformer champions building melee only or ranged only items get those effects accordingly, though at reduced power in ranged.
Adc items could have counter balance conduit items. Inverse versions of Ardent, knights vow, zekes to make adcs get larger spikes next to their supports
mages need a lot of work in itemization, the same few builds are still viable. They no longer have the utility they once did. Full overhaul should be considered with the golden standard being protobelt or zhonyas in 'unique activateable effects"
Mage assassins and mage fighters need a set of items each, even if you just mirror AD items to a fault and rebalance them. this needs to be done immediately.
Sum spells, attach them to boots instead of item slots. No early game cheese just magic boots. change your shoes if you need to change your spells. Smite wouldjust be on a jungle item.
Random skin option: If you own a pool of skins for a champ, pick 'random' it'll pick for you, if the picked skin has chromas that you own, one random chroma might be applied.. or the skin base color
Emote pages: Lemme save that shit
Rune pages saved to champs
Change how slow stacking AND tenacity stacking work,
Toxicity: Increase social elements in client. More chat rooms, competitions, better custom game interface including super casual mode for dropping in and out of a permanent mode, or super intensive things like deciding allowed items/champs/used map/ number of players and number of teams, doom bots, draft type, starting level/starting gold. end goal could be If i want to make a 12 player ffa bloodmoon map with nautilus as the only champ allowed and only crit items allowed then let me.
Allow for a skin market with skins i have but don't want being tradeable for skins I cant get that others have. Example: My riot nasus for trade for your infernal akali or something, all trades would consume tokens, tokens are earned by playing matches, so the system would be hard to abuse
Custom skin community fostering: let people make skins, these skins would be voted on by the community, the ones that make it in are sold, riot gets half and the skin creator gets half. (pretty fucking amazing deal for both sides tbh)
Achievements, More shit to show off, unlock, get x damage while playing as darius, or win x games with zero deaths. all sorts of things from "Play crittlesticks andcarry" to "Deal most damage on your team x times".
More poro pets: Just little vanities
map skins, if you have a map skin you can suggest it on pregame, everyone votes for their team's half of the map. Two map skins per game with river as dividing line. Maybe it's project textures vs snowdown? Could be cool
Custom announcers: Let's say you're playing , you get the draven announcer. anything you do is announced by draven to everyone, if you get a penta, draven says it's a penta. If your lane mate has the SG ahri one, then everyone hears about their exploits from SG ahri
anyone without an announcer has their stuff announced by the announcer of the player seeing it, so the guy with SG ahri hears ahri instead of base announcer, the guy with dravenhears draven.
OTP challenges and game mode: Either an FFA arena, or a pick champ before load screen mode. Rank that champ. challenges would be for advanced things for that champ or inside jokes with that community, be it singed proxy/execute challenge, maybe some riven cancel challenges, or a crittlesticks challenge (Yup) unlock a custom chroma for every x challenges on that champ. maybe wards, definitely icons though. possibly even a basic but unique skin attached to each champ for it.
Opt-in voice chat for pugs: Just let me talk on coms to that salty ass jungler of mine so i can win the game.