You're not wrong.
From my experience, 20% of all games are up to chance. Incompetent teammates have a far larger impact than decent teammates. Depending on who you and your opponents get paired with, some games are guaranteed wins or loses.
That said, I've also noticed a trend that all my friends above Gold rarely surrenders.
Even if your team is 10k behind in Gold, there is still a chance you can win. Forfeiting the game means that you give up that chance. In every game, no matter the circumstance, you need to play as if you can win. If you are unwilling to do this, get out of ranked. You won't ever get a decent rank with a poor attitude.
On the current patch, all it takes is one good team fight in the late game to win. If your ADC is alive, you can break through all 5 towers down mid during the death timers. I have seen many games won while the winning team is in deficient because they managed to aced the enemy team a single time.
The only time I would choose to forfeit would be if my teammates were trash. By that, I don't mean TF players who go 0/3 against Zed or junglers who accidentally gave a double kill due to an outplay. I'm referring to those who are trolling, those who have no idea how to play their champions, and those who are boosted.
From my recent ranked games, I can only think of 2 instances in which I encountered these kind of players in my game. I had a Vayne who kept trying to face check bushes and refused to stay behind back lines. She went something like 1/10. My team still managed to drag the game out to 40+ minutes, but atlas she got caught and we lost. It was probably inevitable, but my team and I still played the game out.
In the other game, I had a Leona one trick who got hard countered. She flamed the entire team after feeding despite everyone else telling her that she can't just engage as Leona against Morgana in lane. I was playing with friends during that game, and we surrendered that one because we didn't want to deal with her.
Unless your teammates are bad, don't surrender. The odds for victory may be low, but giving up is essentially the same as throwing these games. It might not seem significant now, but these losses will accumulate in the long run.