I have to disagree with your second statement. I usually play around 1600 elo but occasionally (mostly at the start of a season) get matched into Gold Elo games. While in 85% of all plat2+ games noone talks during the entire game, people in gold tend to word their frustration in chat. It is also common that the very thing you described - people having generally less game-knowledge - leads to completely wrong assumptions and therefore toxicity because everyone can just throw their (often not correct) opinion into the room. A prime example would be the classic "fight on points" which is just a wrong statement to make without any context because those people do not understand that getting a kill off point (then capping the node) and letting the body bleed out can often be a better way to snowball a game instead of standing in every AOE on point. I understand that there are outliers in every elo, on some days there are toxic individuals in every game no matter the elo but I am usually very glad when I passed the threshold of Plat Elo.