What is the point of demotions?

{quoted}

My performance wasnt bad compared to my other games, in fact the game where i demoted was a good game and my overall performance in the match was very good, so no

Consistency is what matters not one off performance You will not demote off one game; you need a consistent pattern of losses as your mmr rapidly drops, the game gives you significantly worse opponents than your rank should get, and then demotes when you proved even that was too hard.

Dont play ranked looking to win, or even to climb. Play to improve