I've played lol since about 2011 (I think when Urgot came out) and I believe I learned a few things about this game in this time
1. There are good players and bad players. The amount of time you put in to this game contributes to how high you will get, but everyone has their own personal skill ceiling. I've played for 5 years and after a while got to diamond, 2 more friends of mine also got to diamond while others were stuck in gold. We all played for the same amount of time- the only difference was personal talent. If you are stuck in silver/gold/whatever- know there is no reason for it other than that is where you belong. And it is not like I am looking down on you or anything- I have friends who kick my ass in FPS games, but are worse than me in LOL. Whatever, everyone is capable of different things.
2. There are two kinds of "meta game"s. The first one is where you understand the mechanics of the game well enough to recognize things like "role" and "proper builds", and it helps you win more games. The second meta game? Realizing that winning the game doesn't give you anything except boost your ego. Sure, more XP and IP is nice, but eventually those things are meaningless. Whats not meaningless? Queueing up for a normal game and having it filled with nothing but diamond players. It is now impossible for me to play this game and have any sort of fun without 100% tryharding.. and it is my own fault.
Every player in this game can control his elo to some extent, the only thing stopping you is your ego. Take my advice if you wish, and DONT TRYHARD. You are only punishing yourself. The game will get harder and harder, and at the same time more boring. The challenge eventually becomes a chore and you lose interest. None of my friends play anymore except for the occasional aram, and it is exactly because of this. Seeing "victory" at the end of the game is worse off for you in the long run than seeing "defeat". Less immediate satisfaction, but more long term gains.
3. Different games modes teach you different things. ARAM teaches you how to behave in a team fight, and how to dodge skillshots. I only got to diamond after learning these two things (the result of about 500 ARAM games). Dominion teaches you to look at the minimap. I believe I got platinum after doing a lot of dominion games. Don't let the discomfort turn you away. Of course new game modes are less fun at first than summoner's rift, you are used to the rift! Give new game modes a chance.
4. This game is "toxic" by nature. Same as every competitive game. You want to win, and so does your enemy, and this creates TENSION. You can't separate the competition from the game, and where there is competition there will be rivalry. If you see people getting pissed off about a loss or about a bad teammate, don't be surprised. This is MEANT to happen. It is your human nature to be disappointed when you lose, and it is unnatural to hold yourself back. Should you be toxic? Obviously not, but realize why it happens. You are not "weird" for being angry.