It's their matchmaking catching up to Day 1 solo queue players, and it's having a negative effect due to the long term frustrations, which is boiling over to the new players now since they see so many people doing it.
Most of us that solely solo queue and are remotely halfway competent, can easily see how a game is going to play out from the first minute of play or so. Very rarely have I gone into a game thinking "well this will be quick", only to walk away saying "those guys were cracked!"...Very! Very rarely has that happened.
I used to stay in games all the time in the beginning seasons, but after 20K games and over 2 years of playing this game, watching streamers, and content creators, I just know my odds lol
I know that sound selfish, but it's my time and I come to video games for entertainment and to get away from the daily stresses, yet now struggle with the stresses of this games matchmaking.
Bottom line is, if they don't fix their matchmaking it will only get worse. A leaver penalty in Pubs is not the answer IMO especially when code-shoe is so rampant for many players. Hell that's half of the reason I never touch Arenas Modes lol I only have a certain amount of time to play and got so many leaver penalties in Arenas when they rolled the penalty out due to being code-shoe booted.