It's true that there are some games that you're never going to win. Maybe there's a Diamond smurf on their team. Maybe there's someone new to the game on yours. There are also games you're never going to lose, for the same reasons.
What determines whether or not you rise is what you do in the games that are competitive. One metric for how competitive a game is, is the game length. And I'd say, for simplicity, any game that goes over 30 minutes is most likely a competitive one, because if there is such a mismatch, the game tends to end closer to 25 minutes.
Take a good long look at what you do in various situations. One thing that helped me is to focus on the macro game, of taking objectives, of making the team snowball. Nowadays, if ever I'm ahead at the 15 minute mark, I rarely ever let them back into the game. I close it out by 25 minutes.
One thing you see a lot in Silver is a team gets ahead and then decides they want to farm for another 20 minutes. Games that should be won end up getting stretched out, allowing the other team to catch up. A 10K gold lead when it's 25K:15K is far more formidable than a 10K gold lead when it's 35K:25K.