How is Ranked a Fair System?

I get demoted because my ADC is Azir and my mid is Morgana who gets destroyed by Xerath. I get demoted because I can't carry 5 people with the amount of CC in this game. I get demoted because autofill gave someone Mid and someone Jungle, like how are there two autofills on one team? especially in the roles of Middle and Jungle. I get demoted because after all those loses where I do good, I have one bad game and I am punished because of previous losses.

Ranked is such a crapshoot. You either get blessed to have a competent and capable team or you suffer and watch yourself get demoted because of your team and matchmaking.

Like really? It's a nightmare for anyone not gold and above and its an absolute shit show in Bronze.

How is this justified? I guess I got to get good and find a solo carry champ because Jax clearly isn't cutting it even with above 50% win rate. I still find myself DEMOTED.

There should be a system ranking that takes into CS score and deaths as well as other things into account before your demoted. I died 3 times in total in my last loss while everyone else had over 8. I had 100+ CS before 20 (Which is bad but for me good) and bam demoted.