Only since 9.13???? This game has been a towering trash inferno since at least mid season 7. Everything started going downhill around that time and it's progressively gotten worse and worse and worse. This is why the player base has been on a decline for the last 3 years, why league is no longer the #1 stream on twitch, why the LCS viewership has been declining for the last 3 years. This game as been fucked for years; people keep defending it, no matter what Riot does but it has been completely fucked since the juggernaut patch.
Here's the problem. Riot sees a champion doing well, the player base complains and then Riot nerfs that champion out of the game rather than actually addressing the problem, they eliminate the problem. Happened to Lissandra, happened to Olaf, happened to Jayce, happened to Poppy. All of these champs used to have relatively healthy 51-52% winrates and now they're down to about 45-48% and have been basically nerf'd out of play. I remember when I couldn't even play top without going cheese because Jayce was dominating the lane, now; I've seen once Jayce in the last 300 games.
Riot doesn't fix the problem by adjusting counter champs do deal with a certain bully or dominating champ; they just nuke their stats or rework them into complete uselessness, as happened to Kayle. She was in a good place, then the rework happened, then she was slightly better, then Riot nerf'd her early game so hard she's never played.
Riot has created a domino effect and it will destroy their game within the next year or two; and it's pretty much all Tencent's fault. GG