You're not alone. I'm sitting at about 25% win rate over the past 20-30 games, despite my most played champs being around 54-57% win rate. My KDA is alright, and I often get honored, yet I'm still on a consecutive demotion streak. If anything, I should've climbed the way I did, then stayed roughly in one spot if everything was the same. But it isn't. My overall W/L started climbing above 50%, so Riot stepped in and knocked me down. Hard. It was instant: the games suddenly became very one-sided. The team breakdowns were almost always unbalanced and the team with the most low ELO players lost every game, regardless of MMR. I grinded my way to Gold playing support in solo queue, but I get the Silver players on my team while the other team gets the Plats. I know there's an algorithm to "balance" the teams (my 60% gets paired with a 40%) but it's not like I'm going to 1v9 as Nami.
The fact that games are based on W/L isn't fair to players autofilled to an off-role or who main support. Why track data like vision score, objectives, and kill participation if you're not going to use it for rating how much LP to award? I had two griefers/rage quitters for the third game in a row and got demoted, but at least I got another S! My team and the opposing team should all be a similar division, give or take a tier. I get that it's a team game, but it's still solo queue. If someone ints or afks, I still lose LP. They might get penalized, but the damage is already done and I don't get that LP restored.
TL;DR - matchmaking should only be based on current tier, not win %. Losses caused by obvious griefers (the immediately penalized kind) should be equalized.
