Seriously?
You run back even further, alone, miles away from the battle, and just never get caught, and never die.
I fought a vayne who did that. It was bullshit; The only thing on their team that was important to kill and they knew it. Would have lost that game if I wasn't lolwinrammus. We even had an amumu; Nobody can peel rammus and amumu. And the amumu was GOOD.
And that vayne just fucking always kept running back. She'd go whole team fights running away, and we'd never get her. And after we even spent the flashes, she'd run and avoid like, the last two stuns from other people on our team.
And then, finally, come back and shoot people like once or twice.... and then start running again! We never caught her, it was retardedly frustrating.
When we did get her, the 1/100 times, we won, like we knew we would. But I'm guessing that in "high level play" you literally just never get caught as adc.
And it takes an extreme amount of practice to learn to behave this way, but that's probably because the hardest part is trusting 4 other people to make your permanent game of running away count. Which this vayne's team never could, so they lost.
But, we should have won that game at twenty. It actually still got even easier after twenty, but that vayne alone running made it take 45 minutes or more.
So the answer is; You never need peel if you're a good player. You literally just stay even further away from the team fight, and never get caught.
Even watching worlds right now, these people are getting caught by easy tricks. Not to insult Sneaky, but he got gnarred into dragon's wall.
This Vayne wouldn't have suffered that even if that gnar had a flash.