Instead of trying to point fingers...
Instead, realize that playing the "Blame Game" is only going to make people play worse. Yes, your midlaner may be 2/7/1. Yes, your jungler did just screw up a gank. Yes, your ADC is bad at farming.
But you know what won't fix it?
Flaming them for it.
Instead of flaming them, help them learn. And do so kindly (do not do so in a way that's just poorly-disguised flaming!). Use the following guide:
- Reassure them that it's alright.
- Suggest a new course of action. (Do not order! Be nice!)
- Assist them in reversing damage done.
- Praise them for when they do well.
For your midlaner: say they're in a hard matchup, or that it's okay, since everyone messes up (Note if it's a bad pick or toxic champ to fight); Suggest a new build path or strategy (either holding an ability or building some defenses); Help them shut down their laner (gank them, obviously! Make sure they get an assist!); and say that they did well when they do it right ("Good job! :D").
Your jungler: Say it's alright, since jungling can be hard; Suggest a new ganking path or timing for a gank; set up a good gank for them (if you can); and thank them when they gank (even if the opponent doesn't die, as long as they blew a long CD, they helped).
Your ADC: Note that CSing can be hard (especially so against a bully champ); suggest tips you have for CSing; try to keep the enemy laner off of them so they can farm; and tell them they did well when they perfectly CS a wave (or get most of it).
Will you always see improvement? No. Will they always do better? No.
Will it overall improve the environment of League? Yes
Will it help stop your teammates from tilting? Yes
Does it have a good chance of helping them do better? Yes
Will it stop you from flaming them, thereby keeping them from tilting and doing worse? YES
Flaming does nothing aside from pissing your team off. It doesn't help anyone do better, it pisses your entire team off, and has a good chance of causing someone to give up and/or start inting.