I used to always end the season at mid to high silver elo, until this season. I talked to a friend who has hit challenger several times in both solo queue and in 5s, and had him look over 3 replays where I lost, did poorly, and wasn't sure what I was doing wrong. In reviewing it he gave me 3 pieces of advice, and I focused on them this season.

I shot up from silver 4 to platinum 3, and am still climbing quite aggressively, I'll give you the advice he gave me, but I recommend if you genuinely feel that you don't rage, and have played enough games yet not climbing to send replays of games where you lose and aren't sure why to a player at least at high diamond or higher in elo for them to review them and give you their advice. I think you would be surprised just how useful that opinion and analysis can be and how many are willing to do it for you free of charge, just go to a popular chat channel like "low elo" or "trinity force" etc.

For me personally this is what he basically told me:

1) You are mechanically much better than the players in your games, and your warding and vision is far superior, however, you seem too focused on trading to win lanes early which pushes your lane early, and then the jungler repeated ganks your lane. Instead of doing that, simply trade with the opponent and let them push the wave and freeze it, then focus not on killing them or pushing them out of lane, but maximizing the cs difference between you and the opponent of the same role. I switched to this play style and instantly noticed a huge improvement in late game strength in comparison to opponent.

2) You seem to greed too much late game for completing items or getting late dragons. If your team groups you HAVE TO group with them. It doesn't matter if you have 40 minions pushing bot, they grouped mid, you group with them. If by chance they decide to engage even if it was a stupid engage, or an opponent engages then your team will at least have all 5 players there so that you are not at an instant disadvantage. Even if your team simply dances around turrets and no one trades, and those 40 minions drop 2 turrets in a lane against you, it is better than leaving your team to die in a 4v5 as that not only makes you lose a lot, but often leads some teammates to rage at you and tilt instantly losing you the game even when ahead. If you decide to go bottom COMMUNICATE that FIRST, if the team says NO, it means NO. I never used to do this, and I found this alleviated a lot of the later game raging directed at me for not grouping in time, or farming someone else's lane etc.

3) You play way too many roles and champions. It doesn't matter what you play, just pick 2 roles (preferably one being support or jungle as they tend to be less popular), and have 2-3 champions in each of those 2 roles that you pick. Avoid having a permabanned champion as one of those 2-3 champions, otherwise you should have up to 4-5 champions in your primary role, and 2-3 champions in your secondary role. Don't try to be creative and pick for the team comp, or what fits best. You are not an LCS team, and the players at your level make so many mistakes that simply being decent with a champion is more than sufficient to let you climb. As a result of this I took the advice to heart and simply picked my favourite 5 champions to play. It seemed to also help focus me, in seeing what works in certain builds as well and understand matchups better.

These were however advice based on what he saw of my games, but the advice was worded really simply for me, and he made it clear, even showing me examples in games with the time stamps. Just ask someone high in elo to review 3-5 of your losses where you do poorly overall, but aren't too sure what you did wrong. Those are the best to show, not your 22-1 katerina game where you win, since if that was every one of your games you would have no problem. But also don't give the one game you went 0-10, instead give a few standard loss games where you feel you did relatively okay to below average, i.e. don't give any game where your KDA was higher than 2 just as a guideline and see the feedback you get. I think replay.gg now has a site and way for you to instantly record replays and give links to people to watch them, so try that out, or use w.e. replay software you have to ask for advice when uploading your replays.

Good luck.