The Tribunal and report function exist for the community to filter out toxic players.
Do you know why you have the option to report people after game? Because Riot gives you the power to remove players that ruin the experience of other plays, talk trash, intentionally hamper their team, and in some way or another contribute negatively to the game.
The report function is NOT there for you egotistical "perfect" players to spam whenever somebody on your team does bad in a game or does something stupid.
Playing badly--aside from unskilled player, which is just a joke--is not reportable. Stop trying to make yourself feel better about the game by raging to tribunal about somebody who didn't do well. I'm seeing this way too often where teams that start to lose games degrade into 12 year old children that just scream and whine and spam allchat requesting the other team (that doesn't care) to report so and so teammate.
Matchmaking selects RANDOM people and puts them on your TEAM to make games. Stop pretending that you deserve to get que'd with nothing but professional players. You remember that last time to did fed and got frustrated because your team started talking **** to you? You're going to do it to somebody else and they're going to have the exact same reaction--they're going to play worse, teamwork is going to break down, and you're going to lose.
grow up and learn to work with people.
Do you know what teams tell eachother in tournaments and competitive matches? They talk about what they can do with the current situation, what their options are, and coordinate their actions. None of the professional players EVER start raging at a teammate for something that they did in the past.
Know why? Because it's a toxic, useless waste of time.
Stop doing it. All you do when you rage at your teammates is ruin the experience for your entire team, get yourself closer to getting banned, and either make the other people on your team mad or just look like an idiot.
You can't rewind time in game, so focus on what you can do, not what your team should have done.