I'll start this thread with my personal experience. My main account is on Platinum (Moving up and down from plat 3 and plat 5 depending on the streak i get), and there i have a winrate of around 57-60%.
This days i went playing with a friend that was in high silver and i went in with my gold V smurf to help him, and holy mother of hell. Those games are VERY unfair.
First of all, most times the game isn't won by the team who does better, but by the team who doesn't get the dude who just hit level 30 and is playing Yasuo having no idea of what ranked is about. You might say it's not that frequent, but really, check high silver/low gold ELO yourselves. You find those guys on pretty much all the game. And they get stomped because they obviously do not belong that high, but for some reason riot thinks Silver II is a good place to start, while a brand new player who just got to level 30 belongs in bronze 99% of the times (yes there are exceptions but they will climb up anyway)
Then, looking at the game once it has started, there are GIANT skill gaps. And i mean GIANT. I've found gold V people who farm better than platinum guys, and i've found gold V people who average 5 cs/10 minutes on their last 20 games according to opgg. There are so many guys who got 6 or 7 lucky wins on their placements and are in high silver/gold, but who know NOTHING about the game and clearly belong in bronze. I found a LeBlanc who went 1-8 in lane (the kill was from the gank i gave her at level 3) and i went checking his opgg to see if she was just having a bad day or she was a boosted or what the hell was that dude. Found out she was going 1-7-4, 2-8-1, 1-9-0 and 0-11 her last four games. She happened to get lucky and found smurfs on her placements, and she got placed in Gold V. I asked her if she actually thought she belonged on that ELO. She told me she wanted to go to bronze to play games she had a chance on.
Let's get with autofill now. That's not a problem in mid-to-high elo because everyone has one supp they can pick, even if it's an ap dude like Zyra or Brand they actually know what they're doing with him. But low elo... holy shit. I'm sure 99% of the community would rather wait 4 minutes and get a normal support or a premade bot than wait 2 minutes to get a autofill "i can't supp i go yasuo full ad bot" dude. Silver and lower games are just full of the second kind of guy. They are not trolling, they just don't have any supp/don't know how to support. Autofill is a thing that works in high gold/platinum and higher ELO, because there are fewer ppl playing there, but in bronze/silver/low gold? Autofill actually hurts games.
So, i've found myself to have a 55% winratio in low gold ELO. Out of 10 games, the hardest lane loss i had was a 1-3 as Lux against a dude who OTPed yasuo and %%%%ed the hell out of me. How in the earth, playing the same roles and champs i play on plat, can i have LESS winratio?
Simple. Those ELOs are really %%%%ed up, because the matchmaking system is made to fit high elo and pro players. A Diamond guy won't mind going support, because even if he doesn't like playing utility he knows he can go Zyra and play an APC while warding and providing good utility in lane. But a Bronze or Silver guy who can't play support won't do that. He will try and pick something he doesn't know how to play and feed the hell out of the enemy adc. The autofill system is made for high elo. No need to have autofill on a league that has 38% of LoL players (Bronze) or 37% (Silver), because there's so many people searching for games that queues won't be longer than 3-4 minutes anyway. It starts to be neccessary on gold (16%) and it's definetly something you need from Platinum on.
How to fix that? Here are my main ideas:
a) Make unranked accounts who have never played ranked start in bronze-ish MMR and make them move up if they win. With that system, a 10-0 placements will place you somewhere around Gold V (It's VERY stupid to place someone in Platinum V just because he went 10-0 in placements. He might've found ten smurfs in a row. It's not as rare as you can think, try out brand new account and play some placements), and if the dude is good enough, he will move up quickly anyways.
b) Remove autofill from bronze/silver until the matchmaking wait goes over 5 minutes. After 5 minutes of waiting, players can get autofilled support, but in practice this will only happen on very late night hours. No need to autofill players at 4 PM, there are plenty of players going support (Most of them DuoQing, but anyway) there.