I know it is bad to say this
The team is always a problem. It has been that way in silver, in gold, it is this way in plat, and it will be this way in diamond and beyond. I finally got to diamond a few months ago. I've grown a large hate for the typical D4/D3 jungler.
But if I lose more than I win on the long term, then it's my fault. It means I have to learn something new, improve on what I'm already doing and/or quit a habit I didn't know it was bad.
Watch some challenger videos on youtube. Don't skip ahead. Watch the whole lane phase for starters. We always have something to learn from them.
Unfortunately I recently got demoted to Gold 1. Good thing is that I went back to Plat 4 immediately within a day. It seems like my experiments are the cause of my downfall. I am constantly experimenting with better runes or builds that I forgot my basics.
I recently watched how a Challenger Tahm Kench Top One Trick (now D3 or D4 named Samuelz) and looked at his build via his match history. I found out that he had success on what my first strat was, "Win lane, Win Game". Simply dominate the top lane. No tricks, no shenanigans, just dominate using pure skill both micro and macro.
It is really good to go back to your basics when you're stuck. Played 7 games with Tahm and lost once. I did my old build with old runes and old strategy. I was surprised that it worked. Sometimes, less and simpler is better.