The implication of the ranking system is that players with higher rank are better but that really isn't necessarily the reality in low ELO especially. If you get with bad teams, you lose ranking. As you go down in rankings the teams get works and climbing up is impossible because it has nothing to do with your performance. This makes the ranking system frustrating and destructive to morale. It could be changed:
First change the grade system to award points or not points based on your performance rather than grades. For example a max grade could be +10pts and worst grade -10pts. The grade shouldnt be based just on kills and CS as it is now but other things should go in, among them: Damage to Objectives, Kill Participation, Vision Score, Damage Mitigated, Jungle clear CS (for junglers), penalty for support taking CS in laning phase, and KD ratios at various level marks in game rather than just at the end. The last is to account for high deaths that occur after other lanes have fed. In addition, the grading system should punish too much typing, punish cursing at others, and award for for relevant pings if possible but grade you down for spamming. The grading system should be massively enhanced and preferably with some excellent statistical math.
Second, your ranking should be based on your grades and not wins and losses in the game. This would put the emphasis on focusing on your own play to get better rather than just hoping you get lucky and don't get someone playing Zed in support or Sona in mid lane. If the ranking depended on your grades versus other players relative to your rank then the game would truly have a ladder, not a frustrating HORROR show of toxicity that it is now.
Put in something like this and send me an email and I will come back.