How does the ranking system work

You're shit at the game. Thats as simple as it is.

You may have gold elims, but that doesnt matter, you couldve been playing as an elim collecter like Genji, 76, Winston ect.

Kills dont win games, communication, raw skill, accuracy, game sense and wombo combos win games. So practice on this simple things (ie ult wasting/saving, accuracy, teamwork)