Why is rank based on wins instead of player skill?

This has to be the most frustrating thing in ranked. Elo hell. We all know how it is. We get really really close to completing our promo's and then we get a troll on our team or someone who decides to go AFK. Or, we just straight up get some bad people on our team that we should not even be playing with. And we can never rank up!!

What I don't understand, is that if Riot knows that people get stuck in ELO hell, why haven't they done anything to fix it? Why is it, that sometimes no matter how well we do in a match, there is still going to be someone who plays like the belong in Bronze 5 who loses the game for us. It's absolutely frustrating and frankly, I have often given up on League long periods of time because I can't stand how this happens.

So how about, instead of being placed in a rank based on wins, we get placed somewhere based on our performance in game. We already have a system that measures our performance and allows us to gain ranks with that specific champion that we do well with, so why hasn't this been implemented into this game for ranked matches?

I am no professional at this game myself, in fact, I suck. But the most frustrating thing is doing really well sometimes and having the worst possible people on your team ruin the whole match for you with trolling, afking, or just flat out sucking. I swear, 80% of my games consist of me making this face the whole time [slayer-jinx-unamused]