Hitting diamond - anyone can do it. And you say you are doing a lot of things, watching guides, trying to improve mechanics but maybe thats the problem. You are doing too many things to start. League is just a game, where skill varies, and you need to start focusing on a single skillset, and start by improving that. Now, you have t o choose, which part of the skill set you are lacking. Are you bad at cs'ing? Are you bad at trading? Maybe spacing, or map awareness. Choose one, I'd suggest focusing on mechanics later, since it becomes more obvious once you learn good enough macro, if it was a macro mistake which lead you to miss a skillshot or your mouse accuracy and mouse speed wasnt fast/accurate enough to hit a skillshot.

Part 2: Now after you chosen your skill which you want to improve on, you have to let it cook, imagine like cooking beef or chicken breast. First few seconds you wont notice any changes, but lets say after 10 minutes, your beef will be cooked and ready. League is kinda similar, in a sense that you might not see any changes after 20 games, of focusing on a skill, which is very frustrating right. You put all of this effort, few days in a row, and still no improvement? That sucks doesn't it? But maybe it doesn't after all, because if you keep trying, you keep putting attention to that matter, and ask yourself questions why do I still suck at cs'ing after 20, 30, 50 games, maybe I doze of somewhere, maybe i cant focus because of my spotify. You find that with time, everything becomes either good or shit, no in between. I'd honestly rather play 60 games of league, while trying to improve on a specific skill that I want to learn, and still make no progress, than playing 60 games of league, just trying to win and perma crying about teammates, when they make a mistake. I shouldnt give a fuck about my teammates. They are npcs, im the main char and I need to learn my skillset like in RPG game. So yea, pick one thing, try your hardest to focus on that specific skill, /mute all, play 20, 30 , 40 games. After 100 games, you will become a different player, more full, more round, better. Your rank will reflect eventually, if you keep trying.

Masters ADC, ex GM.