Players above your own Division are NOT INVINCIBLE.
I used to get really upset when I found out that my whole team including myself was Silver, and then the enemy team had a couple Plats on it. I'd blame my loss on that.
But today, I was playing Veigar mid against another Veigar, who was newer to the champion. The enemy Yasuo and Ekko got really fed, and they were really good. At one point, I gave the enemy Veigar some pointers on how to play Veigar, since he said it was his first time playing him, and the enemy Yasuo says: "You're Silver 4 why are you giving him tips."
We won the game, and I carried, despite the Yasuo being 4 levels above everyone for most of the game, despite a fed enemy Ekko, and despite having a XERATH JUNGLE (lol). After the game I looked up everyone's stats. Turns out our whole team was Silvers, whereas their team was 3 SIlvers, and then the Ekko was Gold (he was really good so it made sense) and the enemy Yasuo was... Platinum. I'm surprised we won.
So yeah, now I feel like I shouldn't be so upset when I'm matched unfairly, because it is possible to win.