I see your stats and without going into your ranking or anything, your stats aren't that great. I see a lot of negative win rates and your highest ranked win-rate is 44% over almost 70 total ranked games played (according to lolKing, which can be incorrect). Your builds are outdated, there are games where you have under 100cs at 20 min, and you don't ward nearly enough.
Most of the time I see you rushing BT on adc, which used to be the norm, but now BT is to be delayed at least until 4th item as a defensive-ish alternative. I see a lot of Morgana support where you don't purchase a sightstone within a 40 minute game.
I checked a few of your recent ranked games and you're averaging single-digit "wards placed" throughout the matches, which were anywhere from 20 to 40 minutes long.
As support (or sightstone jungler), try to have your "end-game wards placed" to be equal to at least the length of the game in minutes (ex. at least 40 wards over a 40 minute game), and if you keep your warding totem (as a non-sightstone champ), try for 1 ward per 2 minutes game time (2 minute CD throughout the game).
While no, your KDA or even KDR aren't too bad (i would recommend trying to die less though), there are more important things to look at when trying to figure out why you have plateaued in terms of win-rate. Something I tell a lot of the people I coach is that one of the most effective ways to carry a game is simply to ward a lot; vision wins games.
Mind you, I haven't looked at your match-ups, possible champ select or counter-picking, lane synergy, mastery pages, runes, positioning, etc. I feel I have a pretty good understanding of where you sit, in terms of skill.
So you answer your question, yes, I do believe the system in place is (more or less), sufficient in terms of match-making and even though it might be embarrassing or annoying to realize, I also believe you are being matched with appropriately skilled team mates and opponents.
a worthy read if you're interested:
FB: /ifmAries
YT: /tboi3000