It's no secret that you should focus only on your own gameplay. How many games have been lost because of simple mistakes made by you and your teammates? You can't control your teammates' mistakes.
The only thing you can do is focus on your own gameplay. How many stars have been lost simply because you died toward the late game? As a result, your teammates make mistakes, and everything starts going downhill until your Throne gets destroyed.
But in reality, the game could have taken a different turn. You simply need to avoid dying for no reason and contribute your 30–50% of the impact in a game, regardless of your role.
Focus only on your own gameplay. You shouldn't have time to watch your teammates and judge what they're doing or how they're playing. Think one step ahead: what will you do after taking this action?
You shouldn't be thinking, "My jungler is playing badly and doing everything wrong."
No. Focus on your own gameplay, watch the minimap, and keep thinking about how you can help your team destroy the Throne.
There are no perfect players. Improve yourself and focus only on your own gameplay.