Even though it happens on all divisions, lower-rated players tend to overdo it. There’s always someone who always thinks they know better and will unnecessarily write a novel about your bad play in a game. Flaming other players when they make mistakes isn’t constructive or helpful at all, and you should either learn to be quiet or offer useful advice.
Personally when I see other players in my team focus on telling me about every mistake I make in a match it doesn’t help me play better at all, in fact it often makes it even worse because not only do I stop wanting to win I also know they aren’t focusing on winning either. I could always mute abusive players of course but that doesn’t mean they will stop typing and focus on the game, it just means I won’t be distracted by it.
There are hundreds of situations where players type too much in a match and as mentioned it’s usually not helpful to anyone. When your jungler comes to gank and doesn’t succeed or when you die at any point of the game, instead of blaming others for it or gloating to the enemy team do something more constructive with your time: look around the map and see what enemies are doing,what items they’re building, take a look at how good (or bad) their farm is, or how many wards they bought. The only reason why you should open up the chat window is to look up the Dragon or Baron timer and type the respawn time for your team.
Unless you have helpful advice to offer in a friendly way, you shouldn’t focus on your team but instead see how you can either help them or yourself. Think about the items you’ll be building next to counter your opponents or see whether it’s possible to roam some other lane and get kills. You are playing to improve your own skills, not your teams.
I’ve seen countless times how flaming can negatively impact the team’s morale and seal the deal in your match, and I strongly recommend you to focus on your own gameplay and analyze what you can do better to impact the game rather than type. As a practice method I offer you the following advice: when you simply can’t help yourself and just have to offer your opinion in chat, buy a ward for every line of text you type.