Why am I playing with/against people indefinitely better than me?

(This is my first post in the forum so please have patience) https://imgur.com/mPWhsQA https://imgur.com/1jsS3O2 https://imgur.com/HkLpZvD https://imgur.com/BnOmf1N (Wish I could get more pictures but idk how to get match history from more than a week ago) So I'm a simple gold 5 mid lane one trick garbage trying to learn the game and every time I played normal, I either got carried by my teammates or destroyed by the enemy team. I thought it was because I'm trash(which I am) but whenever I played ranked, the enemy team and my team were equally trash as me. Recently I've figured out that I can use op.gg to check the rank of the people in game and in normal matches, I've realized that players I was playing with/against were ranked much much higher than me. I've stopped playing like 6 champions because I thought I suck at those champions and now I realized that it was because this game thought I could handle diamond 5s with champions I've never played before.

Can someone explain to me this game's match making system for normal matches? Also can someone explain to how to not get auto filled? I've legit dodged 6 times in a row and I've never got my primary lane.

Thank you!