Is there a problem with matchmaking?

Right so, this is my second season in gold and I could really use some constructive criticism. Last season I managed to peak at gold 1, before I lost around 19 games in a row and ended up back in gold 5. I quit, and just gave up. Now this season, I won a good few games in a row, got into gold 3 before WHAM. Smacked in the head with another huge lose streak just as my mmr was getting pretty high. How am I meant to escape this? It seems when I lose a shitload of games, eventually my mmr just drops down so ridiculously low that I get matched with really good people, win a few games, before just as my mmr recovers I get matched against people who are 1000x better than me, and my team is full of trolls LOL. Like, the other day, I joined a game and a premade went nunu & Karthus jungle, and we lost. What did I do to deserve that? Or someone afks, or purposely feeds or goes out of their way to ban a champion that I've picked on lobby. Or they're just super tilted from being on a ridiculous lose streak (like me) and end up just under performing and flaming. Like, I genuinely don't know what I can do in these scenarios? And this happens in around 50-55% of my games.

Now I know what most of you will say. You're just shit get better. I get that. I'm not the best player, otherwise I'd be in Masters or something. And recently as I've been tilted I've not played even nearly as well as I think I'm capable of. BUT. Point is, what am I meant to do when a game is literally uncarryable? And yes, some games ARE uncarryable. Even if you snowball your lane, roam and try to help other lanes if your team just isn't up to it, you lose in this elo. Oh and you can bet your life that if you snowball your lane (mid for instance) the two sidelanes will feed like hell. You can't rely on anyone in this elo to be able to actually play their champion to a standard which is good enough to finish a game. Not to mention all the champions I main get banned nowadays, Zed, Yas, LB, and Ekko. Which means I have to end up playing something that I'm not that great at and just play the farm game and try to rely on my team to do something, but it seems that as soon as I get on a losing streak EVERYONE on my team is also on a losing streak? Which, in turn, means they're tilted and we lose. But the stupid thing is? The enemy team will have high golds & plats, on huge win streaks who completely dominate and annihilate the game. -AND- ontop of all of that, there are several champions right now in this patch who are just absolutely and completely busted, but no one I get matched with ever picks them LOL. Is the match making system designed to make it impossible to climb? Because it seems to equal out my win ratio at around 50% or lower, no matter what I do.

Last question, should I change role? I've been a mid and ADC player for two seasons now. And I've been stuck in gold for two seasons. Should I just change role and hope for the best? I was aiming for plat this season, but it really doesn't look like thats going to happen at this rate.

Cheers.