You're worrying way too much about unwinnable games and getting baited into stupid chat. The chat is basically something you need to treat as a kind of Bot-simulation. It's just random gibberish words which you need to react to in the same way as if they were randomly generated in a bot-game. And that means, ignore them. Just close your eyes and imagine how senseless and pointless it would be to get invested in random baby-rage and toxicity that was randomly generated by AI , not human team mates. It'd be fun to get distracted with in a bot game, but imagine it was ranked. It'd just be something to ignore, right? Like... it just does not captivate the attention. It's just ambient noise.

Yet... it seems to captivate your attention. You read this chat, and get very invested in it, and possibly participate in it. This specifically needs to stop because every time you are spending mental energy on non-crucial chat(either reading or writing) is time which is not spent getting better at the game or thinking about your next move in game.

Did you lose that game? Okay. Could you have won it? If no, what's the point of thinking about it any more? You have other things to think about , like the next game, or getting better at League of Legends. If yes, how could you have won it? What's one thing you could have done better. Make a mental note. Make a sticky note. Whatever. Write notes for things you are noticing yourself constantly fail at. When you do this, you will be much more conscious of the mistake, and make progress. When you make progress, you win a teensy tiny bit more. Then the games get harder. And you seem to "make more mistakes", but it's just that the opponents have gotten tougher. Anyway, stop chat, treat getting better as more of a job or school subject, and cut out every single neuron firing that relates to drama in game, or relates to some short term variable like 10 losses in a row. Lose streaks are reality for anyone not smurfing-- the more time you spend thinking about something that is far less significant than the attention you devote to it is, the less time you have for actually improving.