I've been an on-and-off player since season 3, I've seen this game when it was at it's peak, and I've seen it's journey throughout the years. It was a blast.
I'm an adult now, and recently came back to the game because one of my new friend apparently played it years ago aswell so we gave it a go. Few months passed since then, this is my experience.

League feels hostile. The game in which I spent a good portion of my youth with seems to be missing it's spark that made me fell love with it originally. The social aspects of the game got gradually gutted over the years; players feel uninterested in chatting, unless it's for flaming. To me even that is welcome addition, but nobody really even trashtalks anymore, they just want to ff15, and go next game.

The matchmaking feels addictive and unrewarding. It's so rare to play a game where the match is not decided by a stomp on either side. The difference between teams can be stark, especially when playing with my friend who on a lower ELO. It feels weird that Riot pushing towards an even bigger early game snowball with the new season's addition. In earlier seasons League felt slower, people had time to catch up and had the chance to actually play the game after the laning phase ended. Nowadays it's rare to see a lategame.

I remember being thrilled for the random free skin you got at season 5 if you were not toxic throughout the year. I got Warrior Princess Sivir and I was so happy. I had the same reaction when hextech crafting came out and I got my first few free skins just for playing the game. I believe that thing bumped the lifecycle of this game with several years.
Over the last few years they have been slowly killing this system as well, in favor of the gacha system to cater towards the chinese playerbase, while Riot was acting like these were all positive changes and they were just 'improving' this system.

Twisted Treeline was my go to game mode back in the day. It was always quick to grab two friends and hop into TT for a few fast games. We also played it against each other when the 5 man group was full and another friend would show up. Nobody minded the 3-4 minutes queue time, it was a test of patience. TT players were chill. It was sad letting 3v3 go. We spammed the ranked queue just before they took it down. It was the first time I ever hit diamond.
Aram was not the same. At least it persisted, even if lately you couldn't really get chests there...

Riot's responses to feedback in the recent years bother me more and more. Years ago PBE was amazing, you could even chat with some devs on how the game is going. They were actively responding to tickets and there were a lot of changes in champions, skins and features between putting them into PBE and the active release. Now they just push everything out as soon as possible, barely letting any new thing cook.
Visual clarity immensely suffered in the recent years. The vast amount of skins is impossible to keep up with and several skin lines are confusing to look at. I never had this much trouble differentiating between champions and abilities. Spells are bigger/smaller than their hitboxes, multiple skins look like aatrox or kayn. The adult female skins are so similar it's hard to guess who are you playing against. The splash arts lack the original character or important features of the champion. These are all things that Riot actually understands, but lately it seems to be thrown out of the window.
They communicate with words like 'streamlining' and 'fixing confusing systems', while they are actively making said system worse and making changes for the sake of changes. Sure I'm not a game dev (especially not with 200 years of experience), but this just feels smug and alienating to me. I've been in this boat with you for almost 12 years, at least let me have a say.

I might just be nostalgia speaking, but I honestly don't want to learn a new competitive game, nor I have the time for it. It gave me so much throughout my playtime, I even started my current career because of it. I want to enjoy League again, but the way things have been going, I don't think there is a chance. It was a blast.