Is there anyreason why solo ques matchmaking seems a bit imbalanced?

I dont know if i caused this but for some reason in many of my recent games many of the players on my team were ranked silver last season and many of the other players on the enemy team were ranked platinum last season. I dont see how this can be considered fair. I probably am just uninformed as to exactly how the matchmaking works but shouldnt it take into account of last seasons placement into the matchmaking? i can recall one game where i was up against a master tier( last season) player in a solo que game at the rank of gold II. I still won the match but i guess im more or less just looking for answers as to why this happens? Usually in my solo que games I usually have a positive kda and remain positive for the entirety of the game. However i am going to admit that im not perfect and i do make mistakes but i try to own up to them as much as i can. Does that cause the matchmaking system to think that im better than i am and match me with lower level players against teams with higher level players? I guess im just wondering if good performance in solo que determines matchmaking for future games.